01 - Bring a large pot of salted water to a boil. Add the sweet potato cubes and cook until fork-tender, approximately 15–18 minutes. Drain thoroughly and return to the pot.
02 - While the sweet potatoes are cooking, melt the unsalted butter in a small saucepan over medium heat. Continue cooking, swirling the pan occasionally, until the butter foams and develops a golden-brown hue with a nutty aroma, about 3–4 minutes. Remove from heat immediately to prevent scorching.
03 - Add the browned butter, whole milk, and heavy cream to the drained sweet potatoes. Mash using a potato masher or hand mixer until smooth and creamy. Add additional milk, if necessary, to achieve the desired consistency.
04 - Incorporate the salt, black pepper, and optional cinnamon and nutmeg. Stir well to ensure all ingredients are evenly distributed.
05 - Taste and adjust seasonings as needed. Serve warm.