Preheat oven to 200 degrees. Put a wire rack on a rimmed baking sheet and place in the oven.
Put sweet potatoes in a microwave-safe container, cover, and microwave 2 minutes. Stir gently, cover, and microwave 1 to 2 minutes more until pieces are pliable. Let rest 5 minutes covered; pour onto a platter.
In a 4-quart saucepan over medium, heat oil to 375 degrees on a deep-fry thermometer. In a large bowl, gradually whisk the cornstarch into the beer (if you whisk it together all at once, it will get too thick). Working with a handful at a time, dip potatoes into the mixture, letting the excess drip back into the bowl. Add to the hot oil and fry in three or four batches until dark golden brown, 4 to 5 minutes per batch. Transfer fries to oven while cooking the remaining batches.
Place the fries in a large clean bowl, add the Mediterranean Spice mix, and toss to coat. Serve immediately.