First, over medium speed, cream the shortening and butter together. (You can use a hand mixer or a stand mixer.)
Next, add in the cocoa powder and vanilla. Mix together until evenly combined.
On low speed, mix in 2 cups of the powdered sugar.
Then, beat in 1-2 tablespoons of milk to keep the frosting from getting too dry as you combine.
Once that is mixed together, add in the rest of the powdered sugar and stir in a bit more milk until the frosting is light and fluffy.
Can you use heavy cream instead of milk?If you do not have milk on hand, you can use heavy cream but do note that heavy cream is thicker and could require more, to thin it out than whole milk or other types of milk.Have leftover frosting?If you find that you have more frosting than you need, you can store it in an airtight container in the refrigerator for up to 3 weeks!Can you freeze frosting?Did you know you can even freeze your frosting? You can! If it is frozen correctly (airtight, freeze-proof container) it can be frozen for up to 3 months! Let is thaw to room temperature and then whip before using.