Step 1
Preheat the oven to 375 degrees F (190 degrees C). Grease a 9x13-inch baking dish and line a sheet pan with aluminum foil.
Step 2
Heat a large skillet over medium-high heat. Cook and stir sausage in the hot skillet until browned and crumbly 5 to 7 minutes. Transfer sausage to a plate and set aside reserving drippings in the skillet.
Step 3
Melt sausage drippings and 3 tablespoons butter together in the skillet over medium heat. Add onion and mushrooms; cook until soft stirring occasionally 4 to 5 minutes. Stir in 1/4 cup flour and cook for 2 minutes; mixture will thicken as flour cooks. Stir in chicken broth and continue to cook and stir until flour lumps dissolve and mixture begins to bubble about 1 minute. Remove from heat and add sage. Season with salt and pepper.
Step 4
Stir heavy cream into the mixture and add reserved sausage turkey and mixed vegetables. Adjust seasoning if necessary and pour into the prepared baking dish.
Step 5
Combine flour baking powder and salt in a large bowl for topping. Stir in 1 cup heavy cream at first; gradually add remaining cream to form a wet sticky dough.
Step 6
Drop large tablespoon-sized dough balls on top of the meat and vegetable mixture evenly spacing 15 to 16 balls in total.
Step 7
Combine melted butter parsley chives and garlic powder in a small bowl. Brush mixture lightly over each dough ball. Place the baking dish onto the prepared sheet pan.
Step 8
Bake in the preheated oven until bubbly and topping is browned about 45 minutes.
Step 9
Remove from the oven and let cool on a wire rack for about 30 minutes before serving.