1) Cut the outside walls off the jalapeño (leave the stem end intact for a handle), and mince them up, discarding the ribs and seeds.
2) Chop or mash the garlic (if it's roasted).
3) Mix the mashed sweet potato, minced jalapeño, garlic, scallions, brown sugar, allspice, mashed potato flakes, salt, and pepper until thoroughly combined.
4) Heat a large skillet over medium-low heat for a minute or two. When the pan is warm, add the peanut oil. Set up a platter lined with absorbent paper nearby.
5) Use a tablespoon to scoop the dough, then drop it into a bowl containing about an inch-deep layer of mashed potato flakes.
6) Roll around to coat, then press into a round pancake about 1/4" thick.
7) Place the potato cake in the pan, and cook until golden brown, about 2 minutes. Turn over and cook until the other side is golden and crisp.
8) Transfer to the platter to drain briefly; sprinkle lightly with salt, if desired. Serve immediately.
Yield: 1 dozen 2" to 2 1/2" cakes.