Trim and discard tough or discolored stem ends and any bruised spots from mushrooms.
Rinse common mushrooms and drain well. (if using chanterelles, submerge in cool water and gently agitate with your hands to loosen dirt. Drain, rinse under running water, and gently pat dry with a towel.)
Coarsely chop mushrooms.
In a 5-6 quart pan over high heat, stir in bacon until fat begins to render, about 1 minute. Add onion, celery and garlic; stir until onion is limp, about 3 minutes. Add mushrooms and stir often until their liquid is evaporated and mushrooms begin to brown, 15 to 20 minutes.
Add brandy or cognac and stir to scrape up browned bits from pan bottom and sides. Add wine and boil until most of the liquid has evaporated, 1-2 minutes.
Add broth and return to a boil, then cover, reduce heat and simmer, stirring occasionally, to blend flavors, 20-30 min.
Remove from heat.
In a blender, holding down lid with a towel, whirl mixture, a portion at a time, until very smooth.
Pour into a large bowl.
Stir in cream, then salt and pepper to taste.
Chill, stirring occasionally, until soup is at room temperature, 10-15 minutes.
Spoon soup into 6 round souffle dishes or ovenproof bowls (1 1/4 to 1 1/2 cup size; 3 1/2 to 4 1/2" wide) to within 1/2 inch of the rims.
On a lightly floured board, roll each puff pastry shell into a round 1 - 1 1/2 inches wider than top of souffle dishes.
Brush egg in a 1/2" border around the bottom edge (unscored side) of each pastry round.
Carefully drape each round, egg side down, over a dish so that it doesn't touch soup; press edges firmly around sides of dish.
Brush more egg lightly over pastry tops and sides (discard remaining egg or save for another use).
Set dishes at least 1" apart in a 12x17" baking pan.
Bake in a 375°F regular or convection oven until pastry is richly browned, 15-20 minutes.
Serve at once, with sherry-shallot butter, if desired, to stir into portions at the table.