1. Lay the pint of ice cream on its side and slice into four discs using a hot knife. Remove the packaging and put the discs back in the freezer on a tray.
2. Heat a grill to medium-high heat. Place a cast iron skillet over direct heat and add two cups (reserving one) of the huckleberries, zest, lemon juice, orange juice, salt and sugar. Bring to a simmer and let it cook until the berries are popping it begins to reduce. Whisk together the water and cornstarch then slowly drizzle it into the pan while stirring vigorously. As soon as the sauce begins to thicken, stir in the rest of the huckleberries and remove the sauce from the grill.
3. Slice the doughnuts in half like a hamburger bun. Make sure the grill is either super clean or oiled to avoid sticking. Grill the doughnuts over direct heat, cut side down, until bottom starts to caramelize. Flip the doughnuts over and grill the glazed side for about a minute.
4. Place one half of a doughnut on each plate. Top with an ice cream disc and then spoon over the warm sauce. Place a doughnut half on top and sprinkle with mint.