Melt 8 tablespoons of the butter in a large stockpot over medium-low heat. Add the onion, garlic, peppercorns, thyme, and bay leaf; cover and cook for about 5 minutes. Do not let the onion color. Add the tomato paste and lightly "toast" the tomato paste to cook out the raw flavor, then add the tomatoes and 1 cup water, if needed (use only if tomatoes are not ripe and juicy). Simmer over low heat until the tomatoes and onion are very soft and broken down, 30 to 40 minutes.

Purée by passing through a food mill (or use a blender in batches, then strain). Return the soup to the pot. Add the cream and the salt, white pepper, and 2 to 4 more tablespoons butter to taste. Bring the soup to a simmer, then remove it from the heat. Allow the soup to cool for 2 hours or overnight in the refrigerator.

Divide the soup among six 8-ounce soup cups or bowls. Roll out the puff pastry to 1/4 inch thick. Cut out 6 rounds slightly larger than your cups. In a small bowl, beat together the egg with 1 tablespoon cold water. Use a brush to paint the dough with the egg wash and then turn the circles, egg wash-side down, over the tops of the cups, pulling lightly on the sides to make the dough somewhat tight like a drum. (Try not to allow the dough to touch the soup.).

Preheat the oven to 450°F Lightly paint the top of the dough rounds with egg wash without pushing the dough down. Bake until the dough is golden brown, 10 to 15 minutes. Do not open the oven in the first several minutes of cooking, as the dough may fall, serve immediately.