(18 ounce) package yellow cake mix
3 (3 1/2 ounce) packages instant pistachio pudding mix
1 cup water
1 cup vegetable oil
1 teaspoon vanilla extract
1 cup powdered sugar
1 tablespoon butter or 1 tablespoon margarine, softened
2 -3 tablespoons milk
Add the dry cake mix, pudding mixes, water, oil, eggs, and vanilla to a large mixing bowl.
Beat, using an electric mixer, on low speed for 1 minute.
Pour batter into a greased 9-inch bundt pan.
Bake at 350° for 60-70 minutes or until a wooden pick comes out clean.
Cool for 10 minutes in pan; then turn out onto a wire rack to let cool completely.
In a small bowl, mix together the glaze ingredients until smooth.
Drizzle over cake.