-
In a large skillet, saucepan or dutch oven, melt the butter over medium-high heat until foaming subsides. Add mushrooms, garlic, ¾ tsp salt and ⅛ tsp pepper.
-
Cook the mushrooms until they have released most of their liquid, about 5 minutes. Stir in flour and cook for 1 minute. Whisk in broth, scraping up any brown bits from the bottom of the pan. Bring to a boil, whisking constantly.
-
Reduce heat to medium. Whisk in cream and simmer until sauce has thickened, about 5 minutes. Season to taste with salt and pepper.
-
Cook beans in microwave according to package instructions (High 4-5 minutes; let stand 1 minute). Transfer to a colander or salad spinner and drain well.
-
Add the green beans to the pot with the mushroom sauce and toss until evenly coated. Transfer beans and sauce to crockpot.
-
Cook on HIGH 2 hours or LOW 4 hours. Top with canned fried onions immediately before serving.
-
Pre-prep: Make sauce, cooled and refrigerated overnight. Increase Crockpot time to 3 hours on HIGH or 5 hours on LOW (since sauce is cold).