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To make green bean casserole with frozen green beans, thaw and drain the beans, coat them in a thick mushroom sauce, and bake until bubbling. Add crispy onions near the end so they brown without burning. Removing excess water before assembly helps keep the sauce creamy.
This version uses a homemade sauce instead of condensed soup. Frozen cut green beans make preparation straightforward, while fresh mushrooms add texture. It is a practical Thanksgiving side when you want to prepare the vegetables ahead and leave the topping until serving day.
RecipeCrave recipe
Green Bean Casserole With Frozen Green Beans
Side dish · US customary measurements
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Equipment: 9 × 13-inch baking dish
Ingredients for 8 servings · 1× batch
The calculator scales ingredient quantities only. Keep the oven temperature unchanged. Cooking time and pan size require checking; use additional pans for larger batches.
Ingredients
Check the crispy onion label if serving guests with wheat or other food allergies. This recipe also contains dairy and may contain mustard allergens.
Instructions
- Heat the oven to 375°F. Drain the thawed green beans in a colander, then blot with clean kitchen towels. Do not squeeze them into a compact mass; the aim is to remove surface moisture.
- Melt the butter in a large skillet over medium-high heat. Add mushrooms and cook for 7–9 minutes, stirring occasionally, until their released liquid evaporates. Add the chopped onion and cook for about 4 minutes. Stir in garlic for 30 seconds.
- Sprinkle in the flour. Stir for 1 minute, coating the vegetables. Gradually whisk in broth, then milk and cream. Bring to a gentle simmer and cook for 3–5 minutes, stirring, until the sauce coats a spoon. Stir in mustard, salt and pepper.
- Fold the drained beans and 1/2 cup crispy onions into the sauce. Transfer to the baking dish and spread evenly.
- Bake uncovered for 25–30 minutes, until bubbling at the edges and hot in the center. Scatter the remaining onions over the surface and bake another 5–10 minutes. Cover loosely if the topping darkens too quickly.
- Rest for 5 minutes before serving. A chilled, assembled casserole will take longer to heat; check its center rather than relying on the clock alone.
Times and yield are estimates. Adjust ingredient quantities to your needs; cooking times do not scale automatically.
How to avoid a watery casserole
There are two main sources of extra liquid: thawing beans and mushrooms. Drain the first and cook moisture out of the second. The sauce should already be thick before it meets the vegetables. Adding extra flour directly to the assembled casserole can leave dry pockets.
Make ahead and leftovers
Assemble without the topping up to one day ahead and refrigerate promptly. Add the topping during the final minutes of baking. Refrigerate cooked leftovers within two hours and use within 3–4 days. Reheat leftovers to 165°F, checking the center with a food thermometer. USDA reheating guidance.
Frequently asked questions
Can I use frozen beans without thawing?
This formulation is designed for thawed, drained beans. Adding them frozen changes the amount of water and heating time, so thaw them first for a more predictable sauce.
Can I replace the cream with milk?
An equal amount of whole milk will make a lighter sauce. Keep the flour measurement unchanged and simmer until the sauce thickens before assembling.
Can I double the recipe?
Use two baking dishes instead of one very deep dish. Allow space around each pan and check both centers, since oven position affects heating.
For the rest of the meal, browse the RecipeCrave dinner collection.
