Wash and peel the sweet potatoes. Cut them into evenly sized 1–1½ inch cubes so they cook uniformly.

Place the sweet potato cubes in a large pot and cover with cold water by about an inch. Add a pinch of salt and bring to a boil over high heat.

Reduce heat to a simmer and cook until the potatoes are fork-tender, about 12–15 minutes depending on size. Drain thoroughly in a colander.

While the potatoes cook, warm the butter, minced garlic, and olive oil (if using) in a small saucepan over low heat for 1–2 minutes until the garlic is fragrant but not browned. Remove from heat and stir in the cream (or milk) and chopped herbs.

Return the drained potatoes to the hot pot over very low heat for 30–60 seconds to evaporate excess moisture, stirring gently.

Mash the potatoes using a potato masher or ricer until mostly smooth. Pour in the warm butter-herb mixture and fold gently until creamy. For extra silky texture, use an immersion blender in short pulses (avoid overmixing).

Taste and season with salt, pepper, and a squeeze of lemon juice if desired. Adjust cream or milk for preferred consistency.

Transfer to a serving dish, garnish with an extra pat of butter and a sprinkle of chopped herbs, and serve warm.