Pan-Seared Lake Superior Whitefish with Mashed Potatoes and Onion Gravy

By AislePrompt Editorial · Published 2026-06-27 · Updated 2026-06-27

Tender pan-seared Lake Superior whitefish fillets served alongside creamy mashed potatoes topped with savory onion gravy. This American-inspired seafood recipe, ready in about 55 minutes, pairs Lake Superior whitefish fillets, salt, black pepper for a weeknight-friendly dinner that comes together with one pan and minimal cleanup. Each serving lands at about 450 calories and feeds 4, so it slots cleanly into a weekly meal plan and pairs well with a quick salad or grain on the side. Tap "Plan a meal with the AI" below to drop this recipe into your week and send the ingredients straight to Instacart. Nutrition values are approximate, calculated from USDA FoodData Central (fdc.nal.usda.gov) — verify against ingredient labels for any health-driven dietary plan.

Ingredients

• 4 fillets (6 oz each) Lake Superior whitefish fillets
• 1 tsp salt
• 1/2 tsp black pepper
• 3 tbsp unsalted butter
• 2 tbsp olive oil
• 2 lbs russet potatoes
• 1 cup whole milk
• 3, peeled garlic cloves
• 1 large, thinly sliced yellow onion
• 2 tbsp all-purpose flour
• 2 cups beef broth
• 2 fresh thyme sprigs

The pan we’d use for this → Best Nonstick Cookware for 2026: Top 5 Pans + Buying Guide

Instructions

1. Step 1: Peel and cut 2 lbs russet potatoes into 2-inch chunks. Place in a large pot with 3 peeled garlic cloves and cover with cold water. Bring to a boil over high heat and cook for 15-18 minutes until tender when pierced with a fork.
2. Step 2: Drain potatoes and garlic and return to pot. Add 1 cup whole milk and 2 tbsp unsalted butter, then mash until smooth and creamy. Season with 1/2 tsp salt and 1/4 tsp black pepper; keep warm.
3. Step 3: Season 4 Lake Superior whitefish fillets evenly with 1 tsp salt and 1/2 tsp black pepper. Heat 2 tbsp olive oil and 1 tbsp unsalted butter in a large skillet over medium-high heat until shimmering.
4. Step 4: Add the fillets skin-side down and cook for 4-5 minutes until the edges are crispy and golden. Flip carefully and cook an additional 2-3 minutes until fish is opaque and flakes easily. Remove fish and keep warm.
5. Step 5: In the same skillet, reduce heat to medium and add 2 tbsp unsalted butter. Add 1 large thinly sliced yellow onion and sauté for 8-10 minutes until soft and caramelized.
6. Step 6: Stir in 2 tbsp all-purpose flour and cook for 1 minute, stirring continuously to remove raw flour taste.
7. Step 7: Gradually whisk in 2 cups beef broth and add 2 sprigs fresh thyme. Simmer for 5-7 minutes until gravy thickens and coats the back of a spoon. Remove thyme sprigs.
8. Step 8: Serve the whitefish fillets over a bed of mashed potatoes, spoon the onion gravy generously over the top.