Preheat your oven to 375°F (190°C).

Grease a muffin tin or line it with muffin liners for easy removal.

In a medium bowl, whisk together the flour, baking powder, salt, and cinnamon.

In a large bowl, beat the softened butter and sugar together until light and fluffy.

Beat in the eggs one at a time, followed by the vanilla extract.

Gradually add the dry mixture to the wet mixture, alternating with the milk. Mix until just combined.

If using chopped nuts, fold them into the batter gently now.

Divide the batter evenly among the muffin cups, filling each about two-thirds full.

In a small bowl, mix the brown sugar with a sprinkle of cinnamon, then sprinkle this mixture atop each muffin.

Bake for 18-20 minutes, or until a toothpick inserted in the center comes out clean.

Let your muffins cool in the tin for a few minutes before transferring them to a wire rack.