6 cups peeled and cubed raw sweet potato (1/2-inch cubes)
2 1/4 teaspoons coriander seeds
about 7 cascabel chiles, depending on size, enough to make 1 generous tablespoon ground chile (cascabels are smooth-skinned, dark reddish-brown chiles about 3 inches long)
2 tablespoons plus 1 teaspoon real maple syrup
1 generous tablespoon lime juice
1 generous tablespoon orange juice
1 generous tablespoon finely chopped fresh tarragon
2 1/4 teaspoons kosher salt
1 1/4 teaspoons black pepper
In a large saucepan, cover cubes of sweet potato with water, bring to a boil, and cook until tender but not mushy, no more than 9 minutes after the water starts boiling. Pour into a pan of ice water to stop cooking, drain, then mash and set aside.
Toast coriander seeds in an ungreased cast-iron skillet over medium-high heat, stirring occasionally, until lightly browned, 2 to 3 minutes. Grind.
Stem and seed cascabel chiles, then toast in an ungreased cast-iron skillet over medium heat, turning frequently, until crisp, about 5 minutes. Grind.
Mix mashed sweet potatoes with ground coriander seeds, 1 generous tablespoon of the ground cascabels, and remaining ingredients and refrigerate, covered, for 24 hours to let flavors develop. Serve chilled.