Preheat your oven to 350°F and lightly grease a mini muffin tin or line with paper cups.

In a medium bowl, whisk together all-purpose flour, baking powder, and salt.

In another bowl, whisk together milk, egg, and vegetable oil until smooth.

Pour the wet mixture into the dry ingredients, stirring gently until just moistened.

Fold in diced ham, cheddar cheese, and green onions.

Spoon batter into muffin cups, filling each about three-quarters full.

Bake for 12-15 minutes until golden brown and a toothpick comes out clean.

Let muffins cool in the tin for 5 minutes, then transfer to a wire rack.