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Mushroom, Potato & Rice Gratin

Prep 20 min Cook 45 min Difficulty 2/5

Layered mushroom, potato and rice gratin—easy to assemble, creamy, and sliceable. Ready in about an hour.

Why this recipe works

This mushroom, potato and rice gratin is a practical, sliceable casserole that combines tender potatoes with earthy mushrooms and rice for body. It suits cooks who want a low-effort, make-ahead side or simple main.

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Key takeaways

Use a single thin layer of potato per layer for even cooking.
Warm the milk before pouring so it seeps between layers.
Let the gratin rest 10 minutes to set before slicing.

Recipe guide

This mushroom, potato and rice gratin is a practical, sliceable casserole that combines tender potatoes with earthy mushrooms and rice for body. It suits cooks who want a low-effort, make-ahead side or simple main.

A simple layered gratin that uses cooked rice for extra body and a creamy, sliceable texture.

  • Use a single thin layer of potato per layer for even cooking.
  • Warm the milk before pouring so it seeps between layers.
  • Let the gratin rest 10 minutes to set before slicing.

Ingredients

2 cups cooked rice (about 1 cup dry), 3 medium potatoes (thinly sliced ~1/8"), 8 oz mushrooms (sliced), 1 cup milk, 1 tbsp oil or butter for sautéing, salt and pepper, butter or oil to grease the dish.

Method

Preheat oven to 375°F (190°C). Cook rice in 2–2.5 cups water until just tender; drain if needed. Sauté mushrooms in 1 tbsp oil/butter, season. Layer half the rice in a greased baking dish, add a single layer of potato slices, season, and scatter half the mushrooms. Repeat layers. Warm the milk slightly and pour evenly so it seeps through (mixture should come just below top). Cover tightly with foil and bake 40–50 min until potatoes are tender. Uncover and bake 10–15 min to brown. Rest 10 min before slicing.

Tips & Variations

Trim potatoes to even thickness for uniform cooking. Swap milk for ¾ cup milk + ¼ cup cream for richer texture, or add grated cheese on top for a gratin crust. Add herbs (thyme, parsley) with mushrooms and a pinch of nutmeg to the milk for extra flavor.

Ingredients

  • 2 cups rice
  • 3 medium potatoes
  • 1 cup milk
  • 8 oz mushrooms

Instructions

  1. Preheat oven to 375°F (190°C).
  2. Rinse rice and cook in 4 cups water or according to package until just tender; drain if needed.
  3. Peel (optional) and thinly slice potatoes about 1/8-inch thick.
  4. Clean and slice mushrooms.
  5. Lightly sauté mushrooms in a tablespoon of oil or butter until reduced and seasoned with salt and pepper.
  6. Butter or oil a baking dish and layer half the cooked rice evenly in the dish.
  7. Arrange a single layer of potato slices over the rice, season with salt and pepper, and sprinkle half the mushrooms.
  8. Repeat with remaining rice, potato slices and mushrooms to form layers.
  9. Warm the milk slightly and pour evenly over the layered dish so it seeps between layers; add a splash more if needed to reach just below the top layer.
  10. Cover tightly with foil and bake 40–50 minutes until potatoes are tender when pierced.
  11. Remove foil and bake 10–15 minutes more to brown the top slightly.
  12. Let rest 10 minutes before serving to set and make slicing easier.

FAQs

Can I use leftover cooked rice? Yes—leftover rice works well; spread it evenly and ensure it's not clumped so milk penetrates layers.
How do I know potatoes are cooked through? Pierce the top layer with a knife; it should slide through a potato slice easily when done.
Can I make this ahead? Assemble and refrigerate covered for up to 24 hours, then bake an additional 5–10 minutes if still cold from the fridge.