Preheat oven to 350 degrees F. Place 18-20 paper baking cups into cupcake pan. Set aside.
In a stand mixer with the paddle attachment attached, mix vegetable oil, buttermilk, vanilla extract, food coloring, and 2 eggs until combined.
Add in flour, sugar, unsweetened baking cocoa, baking powder, and salt. Mix on low speed for 30 seconds, scrapping bowl as needed. Beat 2 minutes on medium speed, scraping bowl occasionally.
Spoon batter evenly into muffin cups, filing about 2/3 full.
Bake 17-20 minutes, or until a toothpick inserted in center comes out clean. Move cupcakes to a cooling rack. Let cupcakes cool completely, about 30 minutes.
While cupcakes are cooling, let's make the frosting. In a medium saucepan, mix the flour and milk. Cook over medium heat, whisk constantly until the mixture is VERY thick. Make sure to keep whisking. You don't want to burn the bottom. Remove from heat; let cool 10 minutes.
With your stand mixer, beat the sugar and butter on medium speed; until light and fluffy. Slowly add the milk mixture while the mixer is on a slow speed. Once all the milk mixture is added, add vanilla extract and beat on high until smooth.
Fill pastry bag and frost cupcakes.
Enjoy! Store covered in refrigerator.