Peel the sweet potatoes and cut into 1-inch cubes. Place in a large saucepan and cover with cool water so that the water covers the potatoes by 1 inch. Add 1 teaspoon salt. Bring to a simmer over medium-high heat. Continue simmering, adjusting the heat as needed, until the sweet potatoes are fork-tender, about 10 to 12 minutes. Drain, then return the potatoes to the pot.
Add the half and half and chipotle chile powder, cinnamon, nutmeg, and remaining 3 teaspoons salt.
Mash to your desired consistency.
Immediately add the Greek yogurt, maple syrup, and butter. Stir until evenly combined. Taste and adjust spices and salt as desired.
Transfer to a serving bowl and top with thyme. Enjoy warm.
Notes
TO STORE: Refrigerate sweet potatoes in an airtight storage container for up to 4 days.
TO REHEAT: Rewarm leftovers in a Dutch oven on the stovetop over medium-low heat, in a casserole dish in the oven at 350 degrees F, or in the microwave.
TO FREEZE: Freeze leftovers in an airtight, freezer-safe storage container for up to 3 months. Let thaw overnight in the refrigerator before reheating.
TO MAKE AHEAD: Up to 2 days in advance, peel, cut, and boil the sweet potatoes. Refrigerate them in an airtight storage container until you're ready to finish the recipe.
For easy mashed sweet potatoes any night of the week, make a big batch and freeze leftovers in an ice cube tray. Transfer the frozen sweet potato cubes to a freezer-safe ziptop bag. Grab sweet potato cubes as desired and cook directly from frozen.