Preheat your oven to 325 degrees and grease/flour your cake pans (I usually cut a piece of parchment paper the same shape as the bottom of my pan and add that on top of the grease/flour as a further precaution against the cake bottom sticking to the pan).
In your mixer, add your chilled butter, shortening, and sugar. Mix until creamy...the sugar will be fully incorporated.
Add in your extracts.
Combine in a separate bowl, your dry ingredients: flour, salt, baking powder.
Alternating: add some of your dry ingredients, then a bit of the milk, then one egg. Repeat until all ingredients are incorporated. The batter will be thick.
Place batter into the cake pan/pans and bake in the preheated oven for 40-60 minutes.
Keep an eye on it. The lower temperature means longer baking time and each cake size requires different bake times. My 10” round cake 3” in height took over an hour, and my 6” round cake 2” in height took around 40 minutes.
If you do not have butter extract, try replacing it with a different flavor extract of your choice. Vanilla is always a fail-safe choice.
Makes 7-9 cups of batter
Sturdy & Moist White Cake https://www.twistedtastes.com/dessert/sturdy-moist-white-cake/