How does Wilde use food as a way to satirze the aristocracy?
As a society, Victorians were snobby and classicist down to how to hold a fork down, the types of foods they ate, and the amount that they served. More, opulent, excessive, and hyperbolic always meant "wealthy" or "fashionable".
Lady Brackell ate "crumpets" with the Duchess, and the famous cucumber sandwiches are symbols of status.
In the famous showdown between Gwendolyn and Cecily, food made all the difference. Cecily's cake and sugar were "unfashionable" and "unseen in the households of the best families", whereas her bread and butter and her unsweetened tea were apparently the "rage" in London.
Cecily. [Sweetly.] Sugar?
Gwendolen. [Superciliously.] No, thank you. Sugar is not fashionable any more. [Cecily looks angrily at her, takes up the tongs and puts four lumps of sugar into the cup.]
Cecily. [Severely.] Cake or bread and butter?
Gwendolen. [In a bored manner.] Bread and butter, please. Cake is rarely seen at the best houses nowadays.
Cecily. [Cuts a very large slice of cake, and puts it on the tray.] Hand that to Miss Fairfax.
[Merriman does so, and goes out with footman. Gwendolen drinks the tea and makes a grimace. Puts down cup at once, reaches out her hand to the bread and butter, looks at it, and finds it is cake. Rises in indignation.]
Gwendolen. You have filled my tea with lumps of sugar, and though I asked most distinctly for bread and butter, you have given me cake. I am known for the gentleness of my disposition, and the extraordinary sweetness of my nature, but I warn you, Miss Cardew, you may go too far.
The drama caused by these simple elements shows the sarcasm with which Wilde described the idleness and lack of real worries of aristocrats, and their ridiculous and excessive behaviors are mainly represented in Algernon.
Algernon's excesses as well as his living above his means, eating without control, and running away of his debtors are representative of how half of the so-called polite, upper classes of Victorian society actually lived. Algernon is used as a sample of this noble society, and his habits are indeed a mockery of those other aristocrats who lived among above their means, and yet went into debt to entertain, eat, and live in opulence and excess.
Algernon's specific constant eating is a reflection of how he lives his life: To the fullest, literally. Similarly, his hunger is also another reflection of how he lives: Always wanting more.
My favorite satirical episode is in Act I of The Importance of Being Earnest when Algernon eats all the cucumber sandwiches. Algernon has invited his Aunt Augusta to tea. Before she arrives, Jack, who's also there, asks:
Why all these cups? Why cucumber sandwiches? Why such reckless extravagance in one so young? Who is coming to tea?
When Jack tries to eat one, Algernon forbids it. Only he and his aunt can eat them. Jack is confused: why can she eat them but not him? Well, it's because she is a higher class than Jack. They are reserved only for the established rich.
The irony is that Jack eats them all before his aunt gets there. When she asks to be served some tea and cucumber sandwiches, Algernon blames Lane, his butler, who in turn blames the market. "No cucumbers!" "No, sir, not even for ready money."
So, why does Jack eat them all? Does he resent his aunt? Does he want her out of his place as soon as she gets there? Do the rich not only resent the underclass but those who are rich as well? Do the cucumber sandwiches then become an objective correlative, a symbol for his resentment for the elitist Victorian class system? After all, he tries to get out of going to his aunt's parties by inventing his friend Bunbury. So, the sandwiches are like names and false identities: completely superficial status symbols.
In the end, the cucumber sandwiches are connected to money and high society. They're like money itself, and those who have them want them all to themselves.