Heat oven to 350°F. Line 9-inch square pan with cooking parchment paper.
Step
2
In medium bowl, place cookie mix. Cut in butter with pastry blender or two knives until mixture is size of small peas. Add egg; mix until combined. Dough will be very crumbly. Press half of the mixture into pan.
Step
3
In separate bowl, toss blueberries, raspberries, blackberries, granulated sugar and cornstarch. Spread on top of sugar cookie mixture. Crumble remaining dough on top of fruit mixture.
Step
4
Bake 35 to 40 minutes or until topping is golden and fruit filling is bubbly. Cool completely, about 1 hour.
Step
5
In small bowl, beat Icing ingredients with whisk, adding just enough milk to make a thick but pourable glaze. Drizzle over cooled bars. Let stand 20 minutes before cutting. Cut into 4 rows by 4 rows.
Leave extra cooking parchment paper overhanging sides of pan to use as handles to lift cooled brownies out of pan before cutting.
You can substitute frozen fruit for fresh. Do not thaw before using.
