Preheat oven to 350F/180C and line your muffin tin with paper liners.
In a medium bowl combine sifted flour, oats, baking powder, baking soda, salt, sugar, cinnamon and nutmeg.
In a large bowl beat eggs, oil, yogurt and vanilla. Stir in grated carrots and then add in dry ingredients to the bowl.
In a small bowl combine butter, flour, oats, sugar and cinnamon for the streusel topping. It works best if you mix it with your fingers. The streusel topping mixture will resemble cookie dough.
Divide muffin batter evenly among 12 muffins cups and top them with a teaspoon of streusel topping.