For the carrot oatmeal muffins, first preheat the oven to 175 °C. Line a muffin tray with paper cups or grease.
Peel and finely grate the carrots. Mix buttermilk, oil, egg and sugar. Mix flour with baking powder and baking soda. Add hazelnuts, oatmeal, cinnamon and carrots. Then gently fold this mixture into the buttermilk mixture.
Pour the muffin batter into the cups to a maximum height of 3/4 and bake the carrot-oatmeal muffins for about 20 minutes.
The carrot oatmeal muffins can be topped with frosting after cooling.