Preheat the oven to 450 degrees F. Mix 1/4 cup yogurt, the garlic, 2 teaspoons curry powder, 1 teaspoon salt, a few grinds of black pepper and the cayenne in a large bowl. Add the chicken and toss to coat; set aside.
Pierce the sweet potatoes all over with a fork. Bake on a baking sheet until tender, about 25 minutes. Meanwhile, pulse the cereal in a food processor until finely ground; season with salt, black pepper and the remaining 1/2 teaspoon curry powder. Transfer to a shallow baking dish.
Heat 1/2 inch peanut oil in a large cast-iron skillet over medium-high heat until shimmering. Press the chicken into the cereal, turning to coat. Add half of the chicken to the hot oil and fry until golden brown, 3 to 5 minutes per side. Transfer to a wire rack set on a baking sheet. Repeat with the remaining chicken. Transfer to the oven and bake until cooked through, about 10 minutes.
Mix the ketchup with the steak sauce and cilantro. Split open the sweet potatoes; top with the remaining 1/2 cup yogurt and season with salt and black pepper. Serve the chicken with the potatoes and ketchup; top with more cilantro.