Prep the sweet potatoes: Peel and cut sweet potatoes into even cubes. This helps them cook evenly.
Boil or steam: Place cubed sweet potatoes in a large pot with water. Bring to a boil, then simmer until soft (15–20 minutes). Alternatively, steam them.
Roast the garlic: Wrap garlic cloves in foil, drizzle with olive oil, bake at 400°F for 20 minutes until soft.
Mash: Drain the potatoes, return them to the pot, add butter, roasted garlic, and milk or cream. Mash until smooth.
Add herbs and seasoning: Stir in chopped thyme or rosemary. Season with salt and pepper to taste.
Serve: Transfer to a bowl, sprinkle extra herbs on top, and serve warm.