For cake:
1 slow cooker liner
1 box white cake mix
1 3.4 ounce package instant pistachio pudding
3 eggs
½ cup vegetable oil
1 cup sour cream
1 teaspoon pistachio (optional)
For Frosting:
1 3.4 ounce package instant pistachio pudding
¾ cup heavy cream
1 cup softened cream cheese
Line a slow cooker with a slow cooker liner.
In a large bowl mix together cake mix, 1 package instant pistachio pudding, 3 eggs, vegetable oil and pistachio extract and sour cream.
Pour batter into slow cooker and spread evenly.
Line the top of the slow cooker with a few paper towels to absorb any excess moisture.
Cover and cook on high for 2 hours.
Insert a toothpick or knife into the center to check if cake is completely cooked. If it comes out clean it's ready. It if still has wet batter it needs more time.
While cake is cooking make frosting.
Whip together 1 package instant pistachio pudding and heavy cream until fluffy. In a separate bowl whisk softened cream cheese until fluffy, then fold into cream and pistachio.
Remove cake from slow cooker by lifting the liner out. Allow to cool completely then spread frosting evenly on top.