Preheat the oven to 180°C (350°F) and line an 8-cup muffin tin with muffin liners.

Whisk the 50 g caster sugar, 50 g brown sugar, and 70 g melted butter in a mixing bowl until combined.

Stir in the egg and 1/2 teaspoon vanilla extract until the mixture is smooth.

Mix the 120 ml milk and 50 g yogurt together in the second mixing bowl.

Add half the 200 g flour, 1 1/2 teaspoons baking powder, a pinch of baking soda, and 1 teaspoon ground cinnamon to the batter.

Fold gently until just combined, then fold in half of the milk-yogurt mixture.

Fold in the remaining flour mixture and remaining milk-yogurt mixture until no dry flour remains.

Divide the batter evenly among the 8 lined muffin cups.

Sprinkle the cinnamon crumble topping evenly over the muffin batter.

Bake at 180°C (350°F) for 18 to 20 minutes until a skewer inserted into the center comes out clean.

Cool the muffins in the tin for 5 minutes before serving warm or at room temperature.