Instructions

• Preheat the oven to 400°F. Lightly coat an 8×10-inch (or similar 2½‑quart) casserole dish with nonstick spray and set aside.
• Heat a large Dutch oven or other deep, heavy-bottomed pot over medium-high heat. Add 1 tablespoon of the olive oil. When the oil is hot but not smoking, add the sliced mushrooms.
• Cook the mushrooms, stirring occasionally, about 8 minutes, until they are beginning to brown.
• Add the garlic powder, kosher salt, and ground black pepper. Cook about 3 more minutes, stirring, until the mushrooms have browned more deeply.
• Sprinkle the flour over the mushrooms, then drizzle in the remaining ½ tablespoon olive oil. Stir and cook 1 to 2 minutes, until any white bits of flour disappear and the flour looks light golden.
• Slowly pour in the milk while switching to a whisk. Whisk constantly, scraping any browned bits from the bottom of the pot, and bring the mixture to a low, gentle boil.
• Continue whisking very often and let the mixture bubble until it thickens and reduces by about half, about 7 minutes.
• Turn off the heat. Stir in the cooked, shredded chicken, the frozen mixed vegetables (no need to thaw), and the chopped fresh thyme. Taste and add additional kosher salt and/or black pepper if desired.
• Spoon the chicken-and-vegetable mixture into the prepared casserole dish and spread it evenly.
• Drop the prepared Easy Drop Biscuits batter (leave the batter unbaked) by rounded spoonfuls over the top, dispersing the biscuits evenly so some filling shows through.
• Bake in the preheated oven until the biscuits are golden brown on top and cooked through, 25 to 30 minutes.
• Let the casserole cool a few minutes, then serve hot.