For the strawberry-walnut muffins, preheat the oven to 160° hot air. Mix the flour with baking powder, cinnamon and nuts in a bowl.
Wash, hull and dice the strawberries.
Put the egg in a bowl and beat with a tablespoon of hot water. Add the sugar and vanilla sugar.
Gradually add the oil and fold in the yogurt.
Gently fold in the flour mixture and finally fold in the strawberries.
Fill 3/4 of the strawberry-walnut muffin batter into ramekins and bake for about 20 minutes.