Heat the grated cheese in the top of a double boiler. Mix the warm beer with the beaten egg yolks. When the cheese has melted, slowly stir in the egg-beer mixture. Add the cayenne and mustard. Stir until smooth. Chop and toast the walnuts. Slice the apples thinly. Steam the broccoli spears until tender but still bright. Toast the bread. For each serving of rarebit, start with two slices of toast. The general idea is to cover the toast with broccoli and apples, pour cheese sauce over them, and top with walnuts. However, I like to put apple slices between two slices of toast, top with broccoli spears, cover with cheese, and garnish with nuts.