1. Preheat oven to 425°. Unroll piecrust on a lightly floured surface; roll into a 12-inch circle. Cut into 24 rounds using a 2-inch scalloped-edge round cutter. Press rounds into bottoms of ungreased miniature muffin cups. (Dough will come slightly up sides, forming a cup.) Prick bottom of dough once with a fork.
2. Bake at 425° for 4 to 5 minutes or until set. Cool in pans on a wire rack 15 minutes. Reduce oven temperature to 350°.
3. Meanwhile, drain tomatoes well, pressing between paper towels. Combine tomatoes and chopped basil in a small bowl; season with desired amount of salt and pepper. Stir together mayonnaise and next 3 ingredients in a medium bowl. Divide tomato mixture among pastry shells, and top with mayonnaise mixture.
4. Bake at 350° for 18 to 20 minutes. Serve immediately. Garnish, if desired.
Note: To make ahead, bake and cool pastry shells as directed in Steps 1 and 2. Remove from muffin pans, and store in an airtight container up to 3 days. Return pastry shells to muffin pans, and fill and bake as directed.