In a large bowl, sift the flour with the baking powder, baking soda and salt.
In another large microwave-safe bowl, add the butter with the milk, sugar and mix with a balloon whisk or fork for a few seconds until the ingredients are well integrated. Place this bowl in the microwave and heat for 40 seconds so that the butter melts a little more.
Add to the bowl of butter, oil, sour cream, eggs, vanilla extract and beat with the balloon whisk or a fork for 1 minute until smooth and homogeneous.
Add the butter mixture to the bowl with the flour and beat with the balloon whisk or a fork for 1 more minute until everything is perfectly integrated.
Add the chocolate chips and beat just until incorporated. If desired, reserve a few beads of chocolate chips to decorate the muffins at the end.
Cover the mixing bowl with plastic wrap or a kitchen towel and refrigerate for 1 hour so the muffins will have a better texture and will rise more when baked.
When there are 15 minutes left in the hour, turn the oven on at 218° C and place baking sheets or baking paper in a 12 large muffin tin.
Pour the mixture into each muffin tin, filling each one 3/4 full. Decorate with more chocolate chips on top of each muffin if desired.
Bake the muffins at 218° C for 5 minutes, then lower the oven temperature to 180° C and bake for 20 minutes more until lightly browned.
Remove the muffins from the oven and let them cool for at least 10 minutes. Decorate with powdered sugar or whatever you like.