2 tablespoons unsalted butter
2 tablespoons canola or vegetable oil
2 medium carrots, peeled and diced
1 large stalk celery, trimmed and diced
1 medium yellow onion, peeled and diced
4 ounces white mushrooms, wiped, trimmed, and sliced
1 cup frozen pearl onions, defrosted
Salt and freshly ground black pepper
2 tablespoons finely chopped flat-leaf parsley
1 tablespoon fresh thyme leaves or 1 teaspoon dried thyme leaves
1 pound cooked turkey, cut into bite-size pieces (about 4 cups)
1 cup frozen petite peas, defrosted
Preheat your oven to 450°F. Position the rack in the middle of the oven.
Heat the butter and oil in a deep 10-inch cast iron skillet or Dutch oven over medium-high heat until hot. Add the carrots, celery, and yellow onion, and cook until lightly browned, 5 to 6 minutes. Add the mushrooms and pearl onions, and, stirring frequently, cook until the pearl onions are lightly browned, 5 to 6 minutes more.
Stir in the flour and cook until a pale golden color, 1 to 2 minutes. Pour in the stock, stir until blended, and bring to a boil, stirring constantly; then reduce the heat and simmer until the sauce thickens, about 3 minutes. Add the turkey and return the liquid to a boil. Stir in the peas, parsley, and thyme, season to taste with salt and pepper, and keep warm over low heat.