In A Doll's House, what is the "miracle of miracles" Nora mentions?

The "miracle of miracles" is that Torvald Helmer would love his wife Nora as an equal—that is, he must recognize her as a person, not as a "doll wife."

Near the end of Act III of A Doll's House, the "wonderful thing" for which Nora hopes is that her husband will demonstrate an unselfish love for her after he understands her past actions. Such a love would be comparable to the love she has for him, and their living together "would become a true marriage." She hopes that when Torvald reads Krogstad's letter, a wonderful thing will happen: her husband will tell Krogstad, "Publish the thing to the whole world," and he will sacrifice his honor because he understands that Nora procured the loan to enable him to get well in a warmer climate. But this does not occur. Only when he receives the second letter from Krogstad, which promises that no action will be taken, does Torvald forgive her.

NORA: As soon as your fear was over--and it was not fear for what threatened me but for what might happen to you--when the whole thing was past, as far as you were concerned, it was exactly as if nothing at all had happened. Exactly as before, I was your little skylark, your doll....

Since nothing in their relationship has changed, Nora tells her husband that she is leaving, and she returns her wedding ring to him. When Torvald asks her if he cannot be more than a stranger to her, Nora replies,

NORA Ah, Torvald, the most wonderful thing of all would have to happen.... Both you and I would have to be so changed.... That our life together would be a real wedlock. Good-bye.

Nora has no chance for individuality in her marriage, so she parts from her husband and her children in order to discover herself and no longer be a "doll."

In Ibsen's A Doll's House, what miracle does Nora expect at the play's end?

This question is interesting as it suggests that Nora's "wonderful thing" can be understood as a "miracle," which is actually a revealing lens through which we can analyze Nora's desire to be seen, understood and appreciated as a person in her own right.

On one level, Nora's "wonderful thing" describes her hope for a husband who loves her and appreciates her for who she is and not only for her femininity and doll-like appeal. Unfortunately for Nora, this hope is doomed from the start, as evidenced by the title of the play, A Doll's House. Torvald does indeed treat Nora like an empty-headed plaything, and he does not see her for who she is.

When it becomes clear that Torvald does not see Nora in the way that she needs to be seen, she leaves Torvald. Perhaps her following through has actually delivered to Nora  her miracle of freedom and independence. By the end of the play, it doesn't matter that Torvald doesn't see her for who she is; Nora got her "wonderful thing" after all, as she now can see, understand and appreciate her own self for all the potential she has to offer.

In Henrik Ibsen's play A Doll's House, in Act II, when Nora tells Mrs. Linde that a "wonderful thing is going to happen...a wonderful...but" also "terrible"thing"(Act II), she is referring to a two part miracle she is expecting to happen.

The first part of the miracle is that her husband will soon learn of the wonderful sacrifice Nora made for him, all on account of love.

The second part of the miracle relates to what Krogstad has taught Nora to expect as a consequence of her forgery. In the first act of the play, Ibsen draws an interesting parallel between Nora and Krogstad. Krogstad is viewed as a character with a poor reputation. As Krogstad states it, Nora "knows, like everybody else, that once, many years ago, I was guilty of an indiscretion" (Act I). Krogstad further explains that the indiscretion society has been punishing him for, through poor reputation, was exactly like Nora's act of forgery. He too, committed a fraud to try and save his wife's life. Krogstad warns Nora that if Krogstad were to inform her husband of Nora's fraud, Nora's fraud would ruin her husband's reputation. The second part of the miracle Nora expects is that she believes Torvald will gladly accept the fall of his reputation, because he understands that Nora committed the fraud out of love for him.

However, Nora also expects that she will be able to prevent the demise of her husband's character and protect him from the weight of the law. The terrible thing she is also expecting is that she will leave her husband and children and even commit suicide to prevent society from learning about her fraud, thus protecting her husband and children. Nora's plans become evident during her conversation with Krogstad in the second act. Krogstad asks Nora if she had it in "mind to run away from your home...or even something worse" and goes on further to describe her as being found in the river "all horrible and unrecognisable, with your hair fallen out" (Act II). Hence, the miracle Nora expects is two fold and ends in something horrible.

In A Doll's House, how does the "wonderful" miracle Nora envisioned reflect the human condition?

Nora Helmer's final monologue in the play A Doll's House reflects the human condition through which Nora has endured her life as a woman, as a wife, and as a mother in a male-dominated society.

In Nora we see humanity perfectly reflected: she is first and foremost a woman. As such, Nora feels the responsibility that falls on her shoulders to care and nurture her family; to be her husband's exemplary wife, as well as her children's best friend. Here comes her tragically-human flaw: Nora's flawed upbringing led her to believe that the way to do her job of nurturer and lover is by pretending to be someone that would please everyone, and not by being herself.

As a result, Nora incessantly seeks the attention that she feels she would receive by doing exactly as would please all others. In return, however, all she gets is to be treated like a plaything; like the plaything that she is acting out to be.

When it is time for Nora to test her worth as a woman, she does this by forging her father's signature in order to get a loan (from a man that works for her husband) and use the money for much-needed medical care for Torvald. Nora claims that, if her husband ever finds out, he would gladly forgive her miscue; after all, it was all made out of love. However, the fact that she continues to hide what she did tells of a very basic human condition: the fact that we only think that we know those who we love; that we really are not in control of anything regarding others, or ourselves. Whatever will be, will be.

The moment the truth is finally known, Nora's biggest nightmare comes true: she is not only insulted and unappreciated for what she had done, but she had become the "shame" of her husband. It is only after Torvald discovers that no consequences will come as a result of Nora's actions that he does a complete turn-around and pretends that nothing was said. He even has the gall to tell Nora that "she is forgiven" and that things will return to normal.

Here is the moment when Nora wishes for a "really great thing", or for a "miracle of miracles".

Ah, Torvald, the most wonderful thing of all would have to happen...[that] both you and I would have to be so changed that our life together would be a real wedlock. Good-bye.

Nora's human condition continues to manifest through her hopes, her fears, and the fact that nothing is final no matter how much we try to make things stay the way we want them to. She realizes that she had wasted years living a fake life, and pleasing a man that has never really grown out of his comfort zone. When she goes through her epiphany and makes her final decision, she does not even wait to hear Torvald's version of her dream. Her miracle is simply: they would either have to be born again and start over, or they would have to be completely new versions of themselves to tolerate a real marriage. There is no option here; that would never happen. Both, Torvald and Nora, lived their life hiding away emotionally from each other's true selves.

In A Doll's House, what does Helmer mean by "miracle of miracles" at the end?

Helmer's last words, which we are told are said when "a hope strikes him" in the stage directions, are shown to refer back to what Nora says just a few lines earlier:

HELMER: Nora--can I ever be anything but a stranger to you?
NORA: (picks up her bag) Oh, Torvald! Then the miracle of miracles would have to happen.

As Nora says, she and Helmer would have to change so much, and anyway, she doesn't believe in miracles any longer. Thus, the play rather cruelly ends with Helmer repeating this phrase with hope, when his words are cut short dramatically with the final sound of the play: the street door slamming shut and Nora leaving his life, asserting her own independence and determined to fashion her own identity. Helmer is left confronting the impossibility of changing himself to save his marriage, and the reality of how he has treated Nora during their marriage.