This recipe comes to us from Seattle-based chef and restaurateur Tom Douglas.
Prepare pepper-salt: In a small saute pan over medium heat, toast Szechuan and white peppercorns for about 3 minutes, shaking the pan. They will smoke and pop like popcorn, but don't let them burn. Let cool, then coarsely grind the pepper in a spice mill, and combine with salt in a small bowl; set aside.
Place cornstarch in a medium bowl. Heat peanut oil in a wok or large saute pan over high heat until it is just short of smoking. Toss prawns in the cornstarch, and remove excess by shaking coated prawns in a sieve. Add prawns to the wok, and cook for 2 to 3 minutes, tossing a few times to cook through on both sides. With a large spatula, hold the prawns in place, tip the wok, and pour off and discard the excess oil. Add garlic, minced chile, and pepper-salt mixture. Return the wok to the heat, and toss prawns with the spices until spices release their fragrance and coat the shells, about 1 minute.