Preheat the oven to 350ºF (180ºC).
Line 12 regular muffin tins with paper liners or butter/spray the pans.
In a large bowl, mix the dry ingredients: sifted flour, baking powder, salt and sugars. Stir to combine.
Whisk eggs, milk, oil, melted butter and vanilla in a medium bowl. Do not beat, but mix well until no streaks of egg whites remain.
Add the wet ingredients at once to the bowl with the dry ingredients.
Mix until you barely have streaks of flour, but do NOT overmix. It will be lumpy and not completely mixed, and that is fine.
Add the chocolate chips and stir lightly with a rubber spatula.
Divide evenly among the muffin cups or muffin liners.
Bake for 20-25 minutes, until the top is cracked, golden brown and a cake tester or toothpick inserted in the center comes out clean. Don't overbake.
Let cool on a wire rack, eat warm or cool down completely and eat at room temperature.
They are best eaten the day they are made, but you can keep them for a day at room temperature, covered or wrapped.
Store leftovers, covered in plastic wrap or an airtight container, in the refrigerator for a few days or frozen for a month.