Heat milk and butter in a small saucepan over low heat until the butter is melted. Set aside to cool.
Combine water, yeast, and sugar in a small bowl and let it stand until the yeast dissolves and the mixture puffs up.
Combine flour and salt in a large mixing bowl. Add milk and yeast mixtures. Stir to combine.
Knead dough until it cleans the sides of the bowl and is smooth and elastic, about 10 minutes.
Remove dough from bowl and oil bowl lightly. Return dough to bowl, turning to coat with oil. Cover with plastic wrap and set in a warm place until the dough doubles in bulk, about 1 1/2–2 hours.
On a lightly floured surface, roll out the dough 1/2" thick. Stamp out circles with a 3-inch cookie cutter.
Lightly spray a large skillet with cooking spray. Cook muffins over medium-low heat for 10–15 minutes, or until light brown, on each side.