Soak the dried morels in water to cover for 2 hours. Preheat the oven to 425F. Roll out half the puff pastry thinly and line the base and sides of a 10-inch tart pan. Place a large piece of wax or parchment paper over the puff pastry. Fill the pie plate to the rim with dried beans. Roll out the remaining piece of pastry and place it over the bean, trimming the edges to fit the tart pan. With any leftover pastry, cut out 4 small diamond shapes and attach them to the crust with the beaten egg. Place the tart pan in the oven and bake for 40 minutes. Melt the butter in a frying pan and cook the onion until softened, about 5 minutes. Drain the morels and rinse well. Add the morels to the onions and cook for 5 minutes, stirring occasionally. Stir in the cream and cook until thickened, stirring occasionally, about 10 minutes. Season with salt and pepper. Remove the pie from the oven and with a serrated knife, carefully remove the cover from the pie. Remove the wax paper and beans. Pour the creamed mushrooms into the pie crust and replace the cover before serving.
