Set oven rack at lowest level and preheat oven to 450°F. Whisk together buttermilk and 2 teaspoons mustard in a large bowl. Add turkey and toss to coat. Combine cornmeal, flour, cumin, thyme and salt in another large bowl. Roll the turkey strips in the cornmeal mixture.
Brush oil on a rimmed baking sheet, and place in the oven for 5 minutes. Transfer the turkey strips using tongs onto the hot baking sheet and return it to the oven. Bake for 10 minutes, or until the undersides of the strips are golden brown. Turn the strips over and bake until the turkey is golden brown on the outside and no longer pink in the center, 8 to 10 minutes longer.
Combine maple syrup and the remaining 1/2 cup mustard in a small bowl. Serve the sauce alongside the hot turkey fingers.