• Preheat the oven to 425ºF.

Turkey base

• Heat the oil in a medium ovenproof skillet over medium-high heat. Add the garlic, carrots and onions; cook until tender and beginning to brown, about 5 minutes.
• Add the turkey and thyme, and continue to cook, breaking the turkey up with a spoon, until the turkey is cooked through and lightly browned.
• Stir in the ketchup and cook until lightly caramelized.
• Stir the broth and flour together in a small bowl until smooth, and then pour into the skillet.
• Cook until thickened, about 2 minutes. Stir in the peas and season with ¼ teaspoon salt.

Potato topping

• At the same time, place the potatoes in a medium pot and cover with cold salted water.
• Bring to a boil, lower the heat and simmer until tender when pierced with a knife.
• Drain the potatoes and return to the pot over low heat. Stir the potatoes for a couple of minutes to dry them out.
• Add the milk, cheese and scallions, and mash until smooth. Add butter if needed.
• Season with salt and pepper.

Finishing steps

• Swirl the mashed potatoes over the filling, or pipe it if you're comfy doing that.
• Lightly mist with nonstick cooking spray and bake until the potatoes are lightly browned and the turkey filling is bubbly around the edges, 10 to 15 minutes.