Shrimp Mushroom Casserole

The first time I made this shrimp mushroom casserole, it was supposed to be a quick Tuesday dinner but ended up being the meal my husband requested for his birthday three months later. I had fallen in love with casseroles as a comfort food classic, but wanted something that felt special enough for company yet simple enough for a weeknight. The way the creamy sauce bubbles up through the golden panko topping creates this irresistible aroma that fills the entire kitchen.

Last winter, I brought this dish to a potluck when we were snowed in with neighbors, and honestly, I have never seen a casserole disappear so quickly. Everyone kept asking what was in the sauce, and it was just the humble combination of sour cream, milk, and a handful of herbs. One friend even confessed she normally hates mushroom dishes but went back for seconds because the flavors melded so beautifully.

Ingredients

• Large shrimp: I have learned that fresh shrimp really do make a difference here, but if you are using frozen, thaw them completely and pat them dry to prevent watery sauce
• Cremini or button mushrooms: These absorb the creamy sauce beautifully and provide that earthy depth that balances the sweet shrimp
• Sour cream and whole milk: This duo creates the most velvety, luxurious sauce base without being too heavy
• Parmesan and mozzarella: The mozzarella melts into gorgeous strands while Parmesan adds that salty, nutty punch that makes the whole dish come alive
• Panko breadcrumbs: They create this incredibly light, crunchy topping that stays crisp even under the creamy sauce

Instructions

Get your oven ready:

Preheat to 190°C (375°F) and butter your casserole dish thoroughly. I have learned the hard way that those little butter corners are where the good stuff sticks.

Build your flavor base:

Heat olive oil with one tablespoon butter in your large skillet over medium heat. Cook the onion until soft and translucent, about 3 minutes. You want them fragrant, not browned.

Add the mushrooms:

Toss in the sliced mushrooms and sauté until they are golden and have released most of their moisture, around 5 minutes. Stir in the garlic for just one minute until fragrant.

Make the roux:

Sprinkle the flour over the vegetables and stir constantly to coat everything. Let it cook for one minute to lose that raw flour taste.

Create the creamy sauce:

Gradually pour in the milk while whisking furiously to prevent any lumps from forming. Add the sour cream, paprika, salt, pepper, and thyme. Simmer for 2-3 minutes until the sauce thickens enough to coat the back of a spoon.

Add the shrimp:

Gently fold in the shrimp and cook for just 2 minutes until they start turning pink. They will finish cooking in the oven, so do not overdo it now.

Assemble the casserole:

Fold in the mozzarella, half the Parmesan, and fresh parsley. Pour everything into your prepared dish and spread it evenly.

Make the golden topping:

Mix the panko with melted butter and the remaining Parmesan. Sprinkle this mixture generously over the top.

Bake to perfection:

Bake uncovered for 20 to 25 minutes until you see the sauce bubbling up through the edges and the topping is golden brown. Let it rest for 5 minutes before serving.

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This recipe has become my go-to when friends need a meal brought over after having a baby or during a difficult time. Something about the combination of creamy comfort and delicate seafood makes people feel truly cared for, plus it reheats beautifully for days of easy meals.

Make It Your Own

After making this casserole countless times, I have discovered that swapping in Gruyère instead of mozzarella creates this incredibly sophisticated flavor profile. The nuttiness of Gruyère pairs unexpectedly well with shrimp, though I still keep a little mozzarella for that satisfying cheese pull. For extra depth, sometimes I sauté the mushrooms in a little white wine before adding the onions.

Perfect Pairings

A crisp green salad with bright vinaigrette cuts through the richness beautifully, and I love serving roasted asparagus or green beans alongside. For wine, a chilled Sauvignon Blanc or buttery Chardonnay complements the creamy sauce without overpowering the delicate shrimp. Steamed rice is also perfect for soaking up every last bit of that velvety sauce.

Timing Tricks

You can assemble the entire casserole up to a day ahead and keep it refrigerated, just add an extra 5 to 10 minutes to the baking time if it is cold from the fridge. I have also made the sauce and vegetable mixture ahead, then folded in the fresh shrimp right before baking for the best texture.

• If your shrimp are particularly large, cut them in half so they distribute more evenly throughout the casserole
• The panko topping can be mixed ahead and kept in a sealed container at room temperature
• Leftovers reheat surprisingly well in the oven at 160°C (325°F) until just warmed through

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There is something deeply satisfying about a casserole that looks impressive but comes from such humble ingredients. I hope this becomes one of those recipes you turn to again and again.

Recipe FAQs

→ Can I use frozen shrimp instead of fresh?

Yes, frozen shrimp work perfectly. Thaw them completely in the refrigerator overnight or under cold running water, then pat dry before adding to the skillet. Avoid overcooking since they'll finish baking in the oven.

→ What mushrooms work best in this casserole?

Cremini or button mushrooms are ideal for their earthy flavor and firm texture. You can also use shiitake for more depth or portobello for meatiness. Slice them evenly so they cook consistently.

→ Can I prepare this casserole ahead of time?

Assemble everything up to step 7, cover tightly, and refrigerate for up to 24 hours. Add the panko topping just before baking. You may need to add 5-10 minutes to the baking time if baking from cold.

→ How do I know when the shrimp are fully cooked?

Shrimp turn pink and opaque when done. In this method, they start cooking on the stovetop for 2 minutes, then finish in the oven. The final baked casserole should bubble around the edges and the topping should be golden brown.

→ What can I substitute for the panko breadcrumbs?

Regular dried breadcrumbs work, though panko provides a lighter, crispier texture. Crushed crackers or even crushed cornflakes can create a nice crunchy topping. Mix with butter and Parmesan as directed.

→ Is this suitable for freezing?

The finished casserole freezes well for up to 2 months. Cool completely, wrap tightly in foil and plastic, then freeze. Thaw overnight in the refrigerator and reheat at 180°C (350°F) until warmed through, about 20 minutes.