Preheat the oven to 375 degrees Fahrenheit. Grease a muffin tin or line the cups with liners. In a mixer fitted with a paddle attachment (or using a hand mixer), cream the butter until smooth. Add 1 cup of the sugar and mix.
Add the eggs, vanilla, baking powder, and salt and mix. With the mixer running at low speed, add 1/2 of the flour, then 1/2 of the milk, and mix. Repeat with remaining flour and milk. Then add in the chocolate chips.
Use an ice-cream scoop or large spoon to fill the muffin cups 3/4 full. Bake until golden brown, 25 to 30 minutes.
Let the muffins cool in the pan for 5 minutes before turning out. Enjoy immediately or cool to room temperature. Store in an airtight container in the refrigerator for up to 5 days.