Preheat your oven to 400°F.
In a non-stick skillet, heat the olive oil over medium heat. Add the diced onion and minced garlic, and sauté until fragrant and translucent.
Add the lean ground turkey to the skillet. Cook until browned, breaking it apart with a spatula.
Mix in the diced carrot, green peas, and 1 cup of cauliflower florets. Season with fresh thyme, salt, and pepper. Allow the mixture to cook for an additional 5 minutes until the vegetables soften slightly.
While the turkey and vegetable mixture cooks, steam the remaining 1 cup of cauliflower florets until tender, about 8-10 minutes.
Once steamed, transfer the cauliflower to a bowl and mash it with a fork or potato masher until a chunky puree is formed. Season lightly with salt and pepper.
Spread the turkey and vegetable mixture in an even layer in an oven-safe baking dish. Carefully dollop and then spread the mashed cauliflower evenly on top to cover the filling.
Place the dish in the preheated oven and bake for 15-20 minutes, allowing the flavors to meld and the top to develop a slight golden hue.
Remove from the oven, let it cool for a few minutes, and serve warm.