Preheat your oven to 400°F and line a baking sheet with parchment paper.
Peel the sweet potato and cut it into 1-inch cubes. Toss with olive oil, sea salt, and black pepper, then roast for 25 minutes until tender and caramelized.
While the potatoes roast, cut the chicken breast into bite-sized pieces.
In a large skillet over medium heat, melt the ghee. Add the minced garlic and grated ginger, sautéing for 1 minute until fragrant.
Add the chicken pieces to the skillet and cook for 5-6 minutes until browned on all sides.
Stir in the garam masala and turmeric, coating the chicken evenly in the spices.
Pour in the tomato puree and bring to a gentle simmer for 5 minutes.
Reduce the heat to low and stir in the full-fat coconut milk, simmering for another 2-3 minutes until the sauce is thick and velvety.
Divide the roasted sweet potatoes between plates and top with the butter chicken and sauce.