Preheat oven to 350º F. Cover a large baking sheet with foil. Mix bacon with brown sugar and ¼-teaspoon black pepper. Arrange bacon in a single layer and bake 25–30 minutes until cooked and crisp. Drain, cool and chop into small pieces. Set aside.
Cook mushrooms in a non-stick pan over medium heat for 7 minutes, or until tender, stirring often. Set aside.
For fresh or frozen string beans: cook in a microwave safe bowl covered with a bit of water on high for 5 minutes until slightly tender. Drain, cool and chop into ¾-inch pieces. If using canned string beans just drain as they are already cooked.
Stir string beans, candied bacon and mushrooms with remaining ingredients, reserving ⅓ cup onions. Bake uncovered in a casserole dish for 25 minutes, until heated through and sauce is thickened and bubbly.
Top with remaining fried onions and bake 5 minutes more until golden. Let sit 5-10 minutes and serve.
To make ahead: Assemble all ingredients and place in a casserole dish. Can be made 1-3 days ahead of time and stored covered in the fridge. When ready to serve, bake as directed.
Used canned or pre-cooked frozen/fresh string beans to reduce baking time and ensure tender string beans
Condensed cream of mushroom and milk creates the sauce. Use organic for best flavor.
Adding cooked sliced mushrooms adds additional flavor and texture. On that note add in chopped candied bacon as well.
Casserole can be prepped ahead, stored in the fridge, then baked when ready
Bake fried onions into the casserole as well as on garnished on top after baking
Bake just before serving at your dinner. It’s best served warm and crispy.
Leftovers are great and can be stored in fridge up to a week. Simply reheat in a microwave.