Unfold piecrusts; stack piecrusts on a lightly floured surface. Roll into one 12-inch circle. Fit piecrust into a 9-inch pie plate according to package directions; fold edges under, and crimp.
Bake piecrust at 450º for 8 minutes; cool on a wire rack.
Whisk together sugar and next 9 ingredients until blended. Pour into piecrust.
Bake at 350º for 40 to 45 minutes or until center is set, shielding edges of crust with aluminum foil after 20 minutes to prevent excessive browning. Cool on a wire rack. Garnish, if desired.