- Make the marchand de vin sauce: In a 2-quart saucepan, melt butter and lightly sauté mushrooms, ham, shallots, onion, and garlic. When the onion is golden brown, add flour, salt, pepper, and cayenne; cook, stirring, for 2 minutes. Stir in stock and wine; bring to a boil. Reduce heat to medium and cook briefly until slightly thick. Keep sauce warm.
- Make the hollandaise: In a stainless steel or heat-safe glass bowl, vigorously whisk egg yolks and lemon juice until mixture is thickened and doubled in volume. Place bowl over a saucepan containing barely simmering water (or use a double boiler); water should not touch bottom of bowl. Continue to whisk rapidly. Be careful not to let eggs get too hot or they will scramble. Slowly drizzle in melted butter and continue to whisk to make a smooth hollandaise. Remove from heat and season to taste. Cover and keep warm until ready to serve.
- Assemble: Lay a slice of bacon across each rusk and cover with marchand de vin sauce. Top with tomato and egg, then hollandaise.