Preheat oven to 350 degrees.

In a skillet cook the bacon over medium heat, stirring occasionally, until it is just crisp, transfer it with slotted spoon to a paper towel lined plate and pour off all but 1 tablespoon of the fat. Cook the leeks in the fat and the butter over medium low heat, stirring, until they are softened, stir in the cream, and bring the liquid to a boil. Simmer the mixture, stirring occasionally, until it is thickened and the cream is absorbed, remove the skillet from the heat, and stir in the Parmesan, the caraway seeds, the parsley the mustard, the bacon, and salt and pepper to taste.

Spread the filling over the warm egg sponge in an even layer, leaving a 1-inch border all around, roll the roulade jelly-roll fashion, beginning with a long side, and trim the ends on the diagonal. With the aid of the towel and the wax paper transfer the roulade, seam side down, to an ovenproof platter, spread it gently with the butter, and sprinkle it with the Parmesan. Bake the roulade for 10 minutes, or until it is heated through and the Parmesan is melted.