Preheat oven to 400°F (200°C).
In a large skillet, heat olive oil over medium heat. Add onions and cook until translucent.
Add ground turkey to the skillet and cook until browned.
Stir in carrots, peas, and corn. Cook for another 5 minutes.
Sprinkle flour over the turkey and vegetables, and stir well. Slowly add chicken broth and stir until thickened.
Transfer the turkey mixture to a baking dish and spread out evenly.
Top the turkey mixture with prepared mashed potatoes, smoothing out to cover evenly.
Bake in preheated oven for 20 minutes or until the potatoes are golden brown.
Remove from oven and let it rest for a few minutes before serving.