Place 2 C muffin mix in a bowl and create a well in the center. Combine milk, egg, oil and yogurt in a separate bowl. Pour wet ingredients into the well and mix until nearly combined. Add berries or diced fruit and stir until just incorporated. Place a rounded TBSP of batter in each cup of a greased muffin tin. Bake at 400 for 10-12 minutes till the tops spring back when lightly touched. (This makes 24 mini muffins.)