What is the Marquis’ party like?

I think that you are referring to the reception that the Monseigneur holds in Paris. The decadence and extravagance is substantial. The monseigneur has four servants help him drink his chocolate. The Marquis Evrémonde dismisses the monsseigneur for his "haughtiness". He leaves the party basically running down little children with his carriage and throwing a coin to the parent. The party is symbolic of the corruption and decadence that the Monseigneur's money brings.