Preheat oven to 375°F. Spray 12 muffin tins with cooking spray.
Cut croissants in half lengthwise.
Press each half into the muffin tin until it is relatively flat at the bottom and sides. Remove any bits that are sticking out of the tin too far. The croissant base does not need to cover the entire sides but you can use pieces to fill in, if desired.
Chop up green onions into small pieces.
Divide the green onion equally between the muffin tins.
Divide cheese equally between the muffin tins.
Beat together the eggs, milk, salt, pepper and onion powder. Divide equally between the muffin tins. This will not reach the top of the tins and that's okay, they will rise!
Bake in preheated oven for 20mins or until the top springs back when lightly pressed. Allow the mini quiches to cool for 5mins.
Plate and serve!
