Preheat oven to 200°C fan. Line a 12-hole muffin tin.
Whisk flour, baking powder, salt and pepper in a large bowl. Stir in 150g cheese, the bacon and spring onions.
In another bowl, whisk eggs, milk, oil and mustard.
Pour wet into dry. Fold gently with a spatula until just combined — lumps are fine.
Spoon into muffin holes. Top with remaining cheese.
Bake 20-22 minutes until golden and a skewer comes out clean.
Cool 5 minutes in the tin, then transfer to a rack.