Heat oven to 425°. Cut 3 medium peeled sweet potatoes into 1/4-inch-thick fries. In a bowl, combine 1 tablespoon cornstarch and 1/2 teaspoon jalapeno salt; add fries and toss. Arrange fries on two baking sheets coated with vegetable oil cooking spray; coat with more cooking spray. Bake until fries begin to brown, 10 minutes. Remove from oven and flip; spritz with cooking spray and sprinkle with 1 sliced jalapeno. Bake until golden, 8 minutes.