For the tarts
2 cups all purpose flour
2/3 cup powdered sugar
1/4 teaspoon salt
1 cup cold unsalted butter, cut into pieces
For the filing
1/2 pound fresh strawberries
1/2 cup sugar
2 tablespoons lemon juice
For the mousse
1 pound fresh strawberries
juice from 1/2 lemon
1/2 cup sugar
1/2 cup whipping cream
2 egg whites
pinch of salt
Grease with butter, or spray with a nonstick vegetable cooking spray, 6 4-inch tart pans with a removable bottoms.
In a food processor, place the flour, sugar, and salt and process to combine. Add the butter and pulse until the pastry starts to come together and form clumps. Place the pastry in the prepared tart pans and, using your fingertips, evenly press the pastry onto the bottom and up the sides of the pan. Pierce the bottom of the crust with the tines of a fork; this will prevent the pastry crust from puffing up while it bakes. Cover and place the pastry crust in the freezer for 15 minutes to chill.
Preheat oven to 425F degrees and place rack in center of oven.
When the pastry is completely chilled, place the tartlet pans on a larger baking sheet, line each with aluminum foil and fill with pie weights. Bake 12-14 minutes, then remove the foil and weights and bake until the crust is golden brown, an additional 4-5 minutes. Remove from oven and place on a wire rack to cool while you make the filling.
For the filing, slice strawberries very thin. In a small sauce pan, combine strawberries and sugar; simmer until strawberries are the consistency of strawberry jam, approximately 15 minutes, stirring every minute or two. Remove from heat, add lemon juice and let cool.
For the mousse topping, in a blender or food processor, puree strawberries with lemon juice and sugar. In a mixing bowl beat cream until it is stiff. Gradually and gently mix the whipped cream with the berries. In another mixing bowl beat egg whites with salt until stiff. Mix one cup of egg whites into berry and cream mixture, and then gently fold this back into egg whites. Refrigerate for at least two hours.
To assemble, fill each tartlet 1/3 full with the strawberry filing. Using a piping bag fitted with a star tip, fill the remainder of the tartlet with mousse. Garnish with fresh strawberry slice. Refrigerate until ready to serve.