Preheat oven to 350°F. Line a 9×13-inch baking pan with parchment paper. Coat with nonstick spray and set aside.

In the bowl of your stand mixer fitted with the paddle attachment, mix the butter and sugar together on medium speed until creamy. Add the dry pudding mix, eggs, almond extract, vanilla extract, salt, baking soda, and cornstarch and mix for 1 minute until combined, scraping the sides of the bowl as necessary. Turn the mixer to low speed and add in the flour, mixing until just combined.

Spread the batter into the prepared pan and bake for 20 minutes, or until lightly golden at the edges. Place the pan on a wire rack to cool completely.

In the bowl of your stand mixer fitted with the paddle attachment, mix the butter and cream cheese together on medium speed until creamy. Turn the mixer to low and add in the almond extract and powdered sugar. Mix for 30 seconds to combine, then increase to medium and beat for 1 minute until smooth.

Spread the frosting on top of the cooled bars, and garnish with the chopped pistachios.

Cut into bars when ready to serve.