Preheat oven to 325 degrees.
Beat butter until nice and fluffy, continue to beat (lowering speed) and add in sugars.
Stop mixer and scrape the sides of the bowl. Add eggs, 1 at a time, followed by vanilla and almond extract, then oil. Add baking soda, cream of tartar and salt.
Add flour 1 cup at a time, mixing thoroughly.
Roll dough into walnut-sized balls (or drop onto baking sheets using a cookie scoop 2-Tbsp.) and bake on an ungreased cookie sheet for 12 minutes.
Cool cookies 3-5 minutes on the pan then transfer to a rack.
Beat butter with an electric mixer on high speed until fluffy. Add powdered sugar, cocoa, vanilla, and milk*. Beat on low speed until ingredients come together then mix on high speed for 3 minutes, occasionally scraping the side of the bowl with a rubber spatula, until fluffy. *If more milk is needed, add it 1 teaspoon at a time. Fit a piping bag or large plastic storage bag with a 2D frosting tip.
Frost-cooled cookies with chocolate rosettes. (Watch my video to see how I do this)Add sprinkles, if desired.