Gradually add the dry ingredients to the wet ingredients. Mix on low speed until just combined.
Add the milk and mix until smooth.
1/4 cup milk
Fill & Bake
Divide the batter evenly into the muffin cups, filling them all the way to the top. I find it helpful to fill a 4 cup measuring glass that has a pour spout to fill my muffin pans.
Bake at 425°F for 5 minutes, then lower the oven temperature to 350°F (177°C) without removing the muffins. Bake for another 15–18 minutes, or until a toothpick inserted in the center comes out clean.
Cool
Let the muffins cool in the pan for 5 minutes, then transfer them to a wire rack to cool completely.
Make the Glaze
In a small bowl, whisk together powdered sugar, milk (start with 2 tablespoons), and vanilla extract.