Melt 3 tablespoons of butter in a saucepan over medium-low heat. Add the leeks and cook until wilted and lightly browned, about 9 to 10 minutes.

Transfer the leeks to a plate and let cool for 10 to 15 minutes.

Preheat your oven to 400°F (200°C) and line two baking sheets with parchment paper.

In a large bowl, whisk together flour, sugar, baking powder, baking soda, and salt.

Cut the remaining 1/4 cup of cold butter into the dry ingredients until the mixture resembles coarse crumbles.

Stir in the cooled leeks and grated cheese.

Make a well in the mixture and add 3/4 cup yogurt. Mix to form a shaggy dough, adding more yogurt if needed.

Flour a work surface and pat the dough into a 1-inch thick disk. Cut out biscuits and transfer to the baking sheets.

Brush the tops with whole milk and bake for 10 to 15 minutes until golden brown.

Remove from the oven and serve warm.