Combine butter, powdered sugar, and flours in mixer (will be slightly softer/doughier than shortbread typically is).
Spread dough on lined jelly roll pan to a thickness of about 1/4″. (Dough may not be enough to fill entire pan — if not, shape into a rectangle in the center of the pan.)
Bake for 12-15 minutes, until just brown.
Let crust cool for at least 1 hour (should be room temperature before adding topping).
Topping
Whip cream until it is just beginning to peak.
Add granulated sugar and vanilla.
Continue to whip until stiff, being careful not to overwhip.
Add cream cheese and whip until fully combined.
Spread cream cheese topping on crust.
Arrange blueberries and strawberries in flag pattern.