This is a marvelous recipe. I originally cooked it for a group of guests at my mothers home (I was ready for entering the University) & I had been including it (Spinach Gateau) in some of my guests Menus since 1961. It was at MASTERING THE ART OF FRENCH COOKING (Volume I), by Julia Child & Simone Beck. I lost that book recently when I moved from San Juan to Ponce. Fortunately I have FROM JULIA CHILD'S KITCHEN (1970) & it is included at page 104:

Many Layered Omelettew with Multiple Fillings (Le Gateau Omni Omelette)

2 cups creamed mushrooms (sauteed mushrooms folded into a thick well seasoned bechamel sauce enriched with cream)
1 1/2 cups Piperade (sauteed onions, green peppers & fresh tomato pulp seasoned with garlic & herbs)
8 eggs plus seasonings & preferred herbs & sufficient butter for making the omelettes
1/2 cup heavy cream
1/2 cup grated Swiss Cheese
2 tb melted butter

When your fillings are ready, beat the eggs with the herbs & seasonings. Heat the omelette pan with butter & pour in about 1/3 cup egg mixture; let settle, swish about & when eggs are coagulated & stll flat in the pan, dislodge the circular disk of egg onto the buttered dish. Spread with part of one of the fillings. Continue making 6 thin omelette disks in all. Alternate fillings, end with a piperade topping. Pour the cream around, sprinkle the omelette cake with the cheese & melted butter. A few minutes before serving, heat & brown lightly in upper middle of a preheated 400 F oven. Cut like a round cake& serve this spectacular dish.