Preheat the oven to 375°F and prepare a 9x13 inch baking dish with baking spray or parchment paper.
With an electric mixer, cream together butter and sugar for 2-3 minutes on high speed until fluffy. Add in eggs and vanilla and mix well.
Add pudding mix, baking soda, flour, and salt and mix on low speed until combined. Add in white chocolate chips last and gently stir into the dough.
Spread evenly into bottom of baking dish and bake for 15-17 minutes, will be soft and look harder around the edges and slightly underbaked in the middle, just like a cookie. Cool completely before frosting.
For the Frosting:
With an electric mixer cream together butter and powdered sugar until light and fluffy, 2-3 minutes. Add in vanilla and almond extracts, and heavy cream, and mix well.
Spread over cooled bars, then sprinkle chopped pistachios on top. Slice and serve.
Notes
Don't overbake! That makes them dry and crumbly. Using a metal pan will bake the bars a little faster, 15-17 minutes. Using a ceramic or glass pan will take slightly longer to bake, add 3-4 minutes onto the bake time.