Preheat your oven to 350°F and line a 12-count muffin pan with muffin liners. Lightly spray the inside of each liner with non-stick spray.
In a medium bowl, whisk the flour, baking powder, baking soda, and salt.
In a large bowl, use a hand-held mixer to beat the softened butter with the granulated sugar until light and creamy. Add the room temperature eggs, one at a time, and mix until just combined after each. Add the vanilla extract, sour cream, and milk, and mix until smooth. Add the dry ingredients and mix until smooth.
Toss the chocolate chips with flour in a separate bowl and then fold them into the muffin batter.
Scoop the batter evenly into the liners, filling each all the way to the top.*
Sprinkle the top of each muffin generously with coarse or sparkling sugar and bake for 15-17 minutes, or until a toothpick comes out clean.
Let the muffins cool slightly before removing them from the pan. Store leftovers at room temperature in an airtight container for up to 1 week.