1Pre-heat oven to 400F. Oil a 12 cup muffin pan with oil, or use muffin cups. Heat the remaining oil in a skiller, add the leek, and cook stirring over low heat for 2 minutes then remove to cool.
2Sift the flour, baking powder, and baking soda into a large mixing bowl. In a separate bowl, lightly mix the egg, yogurt and melted butter together. Add the cheddar cheese, chives, cooked leek and half the chopped ham. Stir while adding in the salt, pepper and garlic salt. Add the cheese mixture to the flour mixture a little at a time and stir until combines. Do not overstir, it will be lumpy.
3Divide the muffin batter evenly between the 12 cups in the muffin pan, about 2/3 full. Sprinkle over the remaining chopped ham, and transfer to the oven. Bake for 20 minutes or until golden and risen. Remove from oven, cool slightly but serve warm.