Estate-Style Creamy Mushroom Chicken Casserole

By Lauren Mitchell, Test Kitchen Director · Reviewed by AislePrompt Editorial · Published 2026-04-06 · Updated 2026-04-06

A comforting one-pan casserole with tender chicken, earthy mushrooms, and a velvety sauce, inspired by timeless family recipes found in estate sales. This American-inspired one-pot recipe, ready in about 70 minutes, pairs boneless, skinless chicken thighs, olive oil, onion for a weeknight-friendly dinner that comes together with one pan and minimal cleanup. Each serving lands at about 550 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

• 1.5 lb boneless, skinless chicken thighs
• 2 tbsp olive oil
• 1 large, diced onion
• 2 cups, sliced mushrooms
• 3 cloves, minced garlic
• 1/4 cup all-purpose flour
• 2 cups chicken broth
• 1 cup heavy cream
• 1/2 cup shredded cheddar cheese
• 1/2 cup frozen peas
• 1/4 cup, chopped fresh parsley
• 1/2 tsp dried thyme
• 1/2 tsp salt
• 1/4 tsp black pepper

Instructions

1. Step 1: Preheat oven to 375°F. Heat 1 tablespoon olive oil in a large oven-safe skillet over medium-high heat. Season 1.5 pounds chicken thighs (cut into 1-inch cubes) with 1/2 teaspoon salt and 1/4 teaspoon black pepper, then cook until golden brown on all sides, about 5 minutes per side; remove and set aside.
2. Step 2: Add remaining 1 tablespoon olive oil to skillet, then add 1 large diced onion and cook until softened, about 3 minutes. Add 2 cups sliced mushrooms and cook until liquid evaporates and mushrooms brown, about 5 minutes. Stir in 3 cloves minced garlic and cook for 1 minute until fragrant.
3. Step 3: Sprinkle 1/4 cup all-purpose flour over vegetables and stir constantly for 1 minute. Gradually whisk in 2 cups chicken broth, then add 1 cup heavy cream, 1/2 teaspoon dried thyme, and remaining 1/2 teaspoon salt and 1/4 teaspoon black pepper. Simmer until sauce thickens, about 3 minutes.
4. Step 4: Return chicken to skillet, add 1/2 cup frozen peas, and stir to combine. Transfer to oven and bake for 20 minutes until chicken is cooked through and sauce bubbles.
5. Step 5: Remove from oven, stir in 1/2 cup shredded cheddar cheese until melted, then sprinkle with 1/4 cup fresh parsley. Rest for 5 minutes before serving.