Preheat oven to 350 degrees. Line two 12-cup cupcake tins with cupcake liners.

In a medium bowl, whisk together the sugar, cocoa powder, flour, baking soda, and salt.

In a stand mixer fitted with a paddle attachment, pour in the dry mixture you just mixed and add the butter. Mix on low for 2-3 minutes until mixture is grainy in texture.

In a medium bowl, whisk together eggs, buttermilk, vinegar, vanilla. And red food coloring.

Turn mixer to low and slowly add in the wet ingredients. Mix for about 2-3 minutes. (Make sure to scrape down the bowl in the middle so that everything gets mixed evenly.)

Pour mixture into cupcake liners, filling about 3/4 of the way up.

Bake for about 15-20 minutes, or until a toothpick comes out clean.

Let cool and transfer to cooling rack.

In a medium saucepan, whisk the flour and milk until smooth.

Place pan over medium-high heat and whisk continually for about 3 minutes, until very think and bubbling.

Remove from heat and strain through a fine-mesh sieve into bowl. Place a piece of plastic wrap directly on surface and refrigerate for about 1 hour.

After an hour, remove the roux from the refrigerator and let sit at room temperature for about 30 minutes.

After 30 minutes, setup a stand mixer with a paddle attachment. Beat the butter on medium speed for about 3 minutes.

Once butter/sugar mixture is pale and cream, add vanilla and mix until incorporated.

Add the room temperature roux and beat on medium for 10-15 minutes until very smooth and white. Every couple minutes scrap the bowl down. (Beat until all the grainy texture is gone. Test by rubbing a small amount between your fingers. If still grainy beat for a couple more minutes and test again.)

Once completely smooth, the icing is ready to use!