They're okay-I used skim milk.
Overmixing muffin batter activates the gluten in the flour, producing dense, rubbery textures rather than tender crumbs. Controlling physical agitation ensures a light final structure. Incorporating dry components into wet components requires a gentle folding motion until just combined.
Allow the baked goods to cool completely on a wire rack before extraction. Proper cooling lets residual steam escape and sets the structure.