Step 1

Heat oven to 350°F. Grease bottom and sides of an 8-inch square pan.

Step 2

In medium bowl, mix butter, flour, and 1/4 cup powdered sugar with a pastry blender or two knives until mixture becomes crumb-like. Press evenly into bottom of pan.

Step 3

Bake 20 to 25 minutes or until edges of crust begin to brown. DO NOT over bake.

Step 4

Meanwhile in medium bowl, beat all filling ingredients with electric mixer on medium-high speed until smooth.

Step 5

Pour filling mixture over warm crust. Return pan to oven; bake for an additional 25 minutes or until filling is set.

Step 6

Cool completely before frosting.

Step 7

In small bowl, beat butter and 1 1/2 cups powdered sugar with electric mixer on low speed until blended. Add remaining ingredients; beat on high speed until well blended. Spread frosting over filling.

Step 8

Cut into 4 rows by 4 rows. Serve chilled or at room temperature.