Preheat the oven to 400 degrees Fahrenheit.
Grease your donut pan and set aside. Even if your pan says it's non-stick, still grease it. Mine is non-stick, but alas, the donuts stick if I don't grease it! In a medium bowl, whisk together all wet ingredients. (First 5 listed)
Whisk in the dry ingredients, making sure to spoon and level the flour, don't pack it in.
Use a spoon to add the batter to the prepared donut pan or transfer the batter to a ziplock bag, cut off the tip and pipe the bater into the pan.
Bake for 9-11 minutes, 10 is perfect in my oven, but all ovens are different. Check with a toothpick, it should come out clean with a few moist crumbs.
Remove from the oven and let cool for about 20 minutes.
Add all ingredients for the frosting to a bowl (start with 1 tablespoon of oil and add a second as needed to thin) and melt in the microwave using 20 second increments, stirring between each until fully melted.
If using vanilla, simply whisk all ingredients together until smooth, adding a few drops of food coloring if desired.
Dip the top of the donut (I use the part that was touching the pan as the top, but either end can be considered the top!) in the frosting.
Add sprinkles on top if desired & enjoy!