Preheat your oven to 450 degrees F. Line your muffin tin with liners (I love using tulip liners to really play the "bakery style" part).
In a large bowl, add the flour, baking powder, baking soda, and salt. Whisk until combined and then set aside.
In another large bowl, add the butter, oil, sugar and eggs. Whisk until combined and a little frothy. Whisk in the sour cream, vanilla and milk. Pour the wet ingredients into the bowl with dry ingredients and fold together with a spatula until minimal lumps remain. Try not to overmix. Add in the chocolate chips and fold together again.
Using a cookie scoop, measuring cup or ladle, pour the batter into the liners, filling 3/4 the way. Sprinkle with extra chocolate chips. If using, sprinkle with coarse sugar for that full on bakery effect!
Place in the oven and bake at 450 for 8 minutes, then reduce the heat to 350 and bake for another 15-20 minutes or until a toothpick is inserted in the center and it comes out clean.
Remove from oven and allow them to rest in the pan for a few minutes and then remove and transfer to a wire rack to fully cool.
Once cool, store in a closed cake dish, or an air tight container.