Melt over mid-high heat in large skillet 4 tbsp. of butter. Sauté mushrooms until limp and very little liquid remains. May add pepper to taste. Pour 1/2 cup of the Champagne over mushrooms and cook until liquid is reduced by half, about 2 to 3 min. Remove mushrooms with slotted spoon and reserve liquid (should be about 1/4 cup of liquid).
Prepare Puff Pastry Sheet according to package, for MINI NAPOLEONS, but cut each of the 3 strips into 2 not 4 rectangles. Split cooked pastries into 2 layers, making 12 layers in all.
Prepare white sauce mix according to package directions (or make your own) using 2 cups milk and 1/4 cup reserved liquid.
In medium size skillet melt 2 tbsp. butter and fry the 6 eggs until the whites of the eggs are set. Add remaining ½ cup of Champagne to skillet. Cover skillet with lid and cook until eggs are firm, or desired firmness.
To assemble: Place one pastry layer on each of the six plates, browned side down. Divide the mushrooms evenly over each, reserving some for garnish. Add egg to each and top egg with slices of smoked salmon, allowing the salmon to extend over the egg and out from under the next pastry layer you are going to add.. Place last pastry layer on top. Pour sauce over each, garnish with mushrooms around base and top with a little Caviar and parsley if desired. Serve immediately.