In a large bowl, whisk together flour, sugar, chipotle, and salt. Using a pastry blender or 2 forks, cut in cold butter until mixture is crumbly and butter is the size of peas. Stir in ham.
In a small bowl, whisk together sweet potato and buttermilk; stir into flour mixture just until dry ingredients are moistened.
Turn out dough onto a lightly floured surface, and gently knead just until dough comes together, 4 to 6 times. Gently roll or pat dough to a 1-inch thickness. Using a 2½-inch cutter dipped in flour, cut dough, without twisting cutter, into 12 rounds, gently rerolling scraps as needed. Place biscuits in a 12-inch cast-iron skillet. Freeze for 15 minutes.
Preheat oven to 450°.
Bake until golden brown, 15 to 20 minutes. Brush with melted butter; serve warm with butter and syrup.
Notes
For cooked sweet potato, prick a scrubbed large sweet potato all over with a fork. Microwave on high until tender, about 5 minutes. Halve potato lengthwise, and let cool completely. Mash flesh with a fork.
Recipe by Southern Cast Iron at https://southerncastiron.com/sweet-potato-and-ham-biscuits/