1. Preheat the oven to 375 degrees F.
2. Heavily grease a muffin tin with nonstick spray.
3. For the caramelized onions – In a large nonstick pan melt the butter over medium heat.
4. Add in the onions to the pan with the salt and pepper.
5. Stir the onions to get them coated with the butter; turn the heat down to low.
6. Continue cooking the onions over a low heat stirring it every 5 minutes for 30 minutes.
7. Pour in the balsamic vinegar. Stir continuously until all of the liquid in the balsamic is evaporated, turn off the heat, and set it aside.
8. For the batter – In a bowl whisk the eggs and milk together.
9. Stir in the Bisquick until well combined. Stir in the onions and half the cheese.
10. Evenly divide the mixture between the muffin tins.
11. Bake for 22 minutes at 350 degrees F.
12. Remove the muffins from the tin, place it onto a foil lined baking sheet sprayed with nonstick spray.
13. Top the muffins with the remaining cheese, place them back into the oven, using only the residual heat.
14. Serve Muffin Quiche with mashed potatoes and bacon.
If you’re following a gluten free diet, be sure to use gluten free Bisquick. Also make sure that the nonstick spray that you use does not contain flour. The muffins are easily made in advance. Just before serving put them onto the cookie sheet, add the cheese, and pop them into a 350 degree F oven for a few minutes to melt the cheese.