Heat oven to 325 degrees F. Line a cupcake tin with cupcake liners.

In a medium-sized mixing bowl, add flour, baking powder, salt and box of instant pudding. Whisk or mix together with a rubber spatula. Set aside.

In the bowl of a stand mixer using the paddle attachment or a large mixing bowl with an electric hand mixer, cream butter and sugar on medium speed until light and fluffy. Add vegetable oil and vanilla extract and mix until well blended. While still mixing, add eggs in one at time until completely incorporated. Scrape the sides of the bowl with a rubber spatula as needed.

Add dry ingredients and incorporate with a rubber spatula until most of the dry ingredients are moistened. This step takes seconds and it's okay if there is unincorporated flour. Add milk and mix with hand mixer or in your stand mixer using the paddle attachment on the lowest speed for 30 seconds. Scrape the sides and bottom of the bowl and mix for another 20 to 30 seconds. The cake batter should be smooth except for the pistachios from the pudding.

Fill cupcake liners with 1/4 cup of cake batter. Bake for 20 to 22 minutes or until a toothpick inserted into one of the cupcakes comes out clean. (If using a 3 Tablespoon cookie scoop to portion out cupcakes, bake for about 16 to 18 minutes.)

In the bowl of a stand mixer using the paddle attachment or a large mixing bowl with an electric hand mixer cream together butters and shortening until well blended. Add vanilla and mix well.

Add powdered sugar in two batches, in halves or thirds and mix well at low speeds. Be sure to cover the stand mixer with a clean towel or it may go everywhere. Scrape down the sides with a rubber spatula.

Add milk one tablespoon at a time and blend. Scrape down the sides of the bowl in between adding milk. Stop adding milk until you have reached the desired thickness. For thinner icing, add even more milk. Blend for 5 to 6 minutes. Store buttercream in the refrigerator when not in use.

Use a decorator bag and tip to frost the cupcakes. If not frosting the cupcakes the same day, store them in a closed, airtight container and frost and serve them within 24 to 48 hours.

You can use pure vanilla extract in your buttercream but you won't be able to get a bright white icing if you do.