In a deep-fryer or heavy-bottomed pot, heat enough vegetable oil to come halfway up the sides of the pot, to 350 degrees F.
In a small bowl, whisk together the maple sugar, black pepper, salt, and yellow curry. Reserve.
Scrub the sweet potatoes clean. Cut in half and then into 12-inch thick wedges. When oil is hot, reduce heat to medium-high and carefully put half of the wedges in the oil. Cook turning occasionally to brown on all sides, about 10 to 12 minutes. Remove to a paper towel lined colander to drain. Sprinkle the fries with some of the reserved spice mixture. Cover with another paper towel to keep warm. Repeat with remaining wedges.
Transfer the wedges to a serving bowl and garnish with green onions.