Preheat the oven to 350F. Roll out the puff pastry on a lightly floured surface and line six 4-inch tartlet molds. Bake for 10 minutes. Remove parchment paper and beans and bake for 10 minutes longer. Keep warm. Melt half the butter in a frying pan and cook the onions over a low heat until softened, about 10 minutes. Stir in the chicken bouillon, salt and pepper and bring to a boil. Reduce heat and simmer covered, for 30 minutes. Blanch the bacon dice in boiling water for 2 minutes. Drain. Fry over high heat until golden-brown, about 10 minutes. In a large saucepan boil the cream hard until reduced by two-thirds. Stir the onions and bacon into the reduced cream. Melt the remaining butter in a frying pan and cook the button onions with the sugar and a little water until golden-brown. In a frying pan fry the foie gras slices until golden-brown, 2 minutes per side. Drain on paper towels. Fill the tartlet molds with the creamed onion mixture. Place a piece of foie gras on top of each tartlet. Broil for 2 minutes. Serve the tartlet surrounded by the baby onions. Sprinkle with the chervil.
