Preheat the oven to 350° and line pan with muffin liners.
For soured milk, put one tablespoon of lemon juice in a measuring cup and add milk to make one cup. Stir and let stand for 5 minutes before using.
In a large mixing bowl cream butter and sugar; beat in eggs, one at a time, beating after each addition. Blend in lemon extract. Gradually stir in lemon peel and soured milk. Finally add the chopped strawberries.
In a separate large bowl, stir together the flour, baking powder, baking soda, and salt.
With a wooden spoon, stir creamed mixture into flour mixture until dry ingredients are just moistened; do not over-mix. Spoon batter into prepared muffin pan, filling each muffin cup about 2/3 full. If you are adding chocolate chips, fold the chips into the mixture.
On the top of each muffin, place one sliced strawberry and sprinkle tops with granulated sugar.
Bake strawberry muffins at 350° for 25-30 minutes. Cool in pan on rack for 5 minutes. Gently turn strawberry muffins onto the rack. Serve warm.