Preheat the oven to 350°F (175°C) and place a rack in the center.
Prick 2 pounds of sweet potatoes all over with a fork and bake directly on the center rack until tender, 45–55 minutes.
Reduce oven temperature to 325°F (160°C). Once cool enough to handle, slice each potato lengthwise and scoop the flesh into a large bowl.
Add 1/4 cup coconut milk, 2 tablespoons maple syrup, 1/4 teaspoon salt, 1/4 teaspoon cinnamon, and a pinch of grated nutmeg. Mash until smooth.
Pecan Streusel
In a separate bowl, stir together chopped pecans, flour, brown sugar, and salt.
Scatter 4 tablespoons of cold cubed butter over the mixture. Cut in with a pastry cutter until coarse clumps form.
Assembly and Baking
Spread the sweet potato mixture into an 8×8-inch baking dish, smoothing the top.
Sprinkle the streusel evenly over the sweet potatoes.
Bake at 325°F (160°C) until the topping is golden and crackling, 25–35 minutes.
Let rest for 5 minutes before serving; drizzle with extra maple syrup if desired.
Notes
Make-ahead: You can assemble the sweet potato mash and streusel topping separately up to a day in advance. Cover each component and refrigerate.Storage: Store leftovers in an airtight container in the refrigerator for up to 4 days or freeze portions for up to 2 months. Thaw overnight and reheat at 325°F until warmed through.