Preheat the oven to 350°F. Grease a 9x13-inch baking dish.
In a large mixing bowl, cream together the softened butter and granulated sugar until light and fluffy.
Add the eggs one at a time, mixing well after each addition.
Stir in the vanilla extract.
In a separate bowl, whisk together the flour, baking powder, and salt.
Gradually add the dry ingredients to the wet mixture, mixing until just combined.
Fold in the chopped pistachios.
Pour the batter into the prepared baking dish and spread evenly.
Bake for 25-30 minutes, or until a toothpick inserted in the center comes out clean.
Allow to cool completely in the pan.
In a medium bowl, beat together the cream cheese, powdered sugar, almond extract, and heavy cream until smooth and creamy.
Spread the cream cheese mixture over the cooled bars.
Chill in the refrigerator for at least 1 hour before cutting into squares.