Preheat oven to 350° F.
Grease the bottom of two 8 or 9-inch round cake pans with shortening. (You can also use a 9x13-inch glass or metal baking dish/pan. Just grease and flour the same way. This recipe also makes 24 cupcakes.)
Trace and cut two circles of parchment paper and press into the bottom of each pan.
Grease the inside of both pans and the parchment with shortening. Flour (or cocoa powder) each pan and set aside. (If you don't have parchment, you can grease and flour without it. It just makes it way easier to get the cake out with it.)
In the bowl of a stand mixer, or a large mixing bowl using a hand mixer, combine flour, cocoa powder, sugar, baking soda, baking powder and salt on low until combined.
Add milk, vegetable oil, eggs and vanilla and mix on medium speed for two minutes. Scrape down the bowl with a rubber spatula if needed.
Add the boiling water or hot coffee and mix on low until combined, scraping down the bowl again when needed.
Pour the cake batter evenly between the two prepared cake pans.
Bake cakes for 30-35 minutes or until a toothpick or cake tester inserted into the center comes out with a few crumbs attached. (I usually start checking the cake after 25 minutes. Some ovens may vary. If you are using a 9x13-inch pan, you may need to add 5-10 minutes to the baking time. Keep an eye on it. If making cupcakes, bake for 15-20 minutes.))
Cool for 10 minutes on a wire rack.
Loosen the sides of the cakes from the pans with a small spatula and turn the cakes out onto wire rack. (Hint: I usually line my wire rack with paper towels and turn the cake out onto them. If the cake sticks, you can just peel the paper towels off.)
Cool completely before frosting.