Step 1Beat butter and powdered sugar on medium speed in electric mixer fitted with paddle attachment 5 minutes. Scrape down sides of bowl.
Step 2Add yolks 1 at a time with mixer on low speed. Add cream and mix at medium speed 1 minute. Turn off mixer and add flour. Mix on low speed until combined. Do not over mix.
Step 3Divide dough in half, wrap in plastic wrap and refrigerate 1 hour.
Step 1Combine brown sugar, flour and cinnamon in bowl and stir until there are no lumps. Set aside.
Step 1Butter and flour 12 (4 1/2-inch) or 2 (10-inch) tart shells. Remove 1 piece of Sweet Dough from refrigerator and roll out 1/4 inch thick. If making individual tarts, cut dough into 6-inch rounds. Line tart shells with dough, trimming any excess dough even with edge of tart shell. Repeat with remaining piece of dough.
Step 2Fill each tart shell half way with Brown Sugar Filling. For individual tarts, dot each with 1 teaspoon butter in pieces and spoon on 3 tablespoons cream. Arrange 1/4 to 1/2 Asian pear, depending on size of fruit, on each tart. Bake at 325 degrees until golden brown, about 35 minutes.
Step 3For 10-inch tarts, dot each with 2 tablespoons butter in pieces and spoon on 9 tablespoons cream. Arrange Asian pear slices on each tart. Bake at 325 degrees until golden brown, 45 to 50 minutes.