Mash garlic with 1/4 teaspoon salt, pepper and ginger to form a paste.
Place pork in a jelly-roll pan or large roasting pan; rub all over with garlic mixture.
Toss sweet potatoes with 1 Tablespoon oil and 3/4 teaspoon more salt in a large bowl. Arrange potatoes in pan around the pork.
Combine the brown sugar, vinegar, soy sauce and remaining 1 tablespoon oil in a small saucepan; brush some of the mixture over the pork. Roast pork and potatoes 10 minutes.
eanwhile, bring remaining soy sauce mixture to a boil over high heat. boil until sauce is thickened, 5 minutes; remove from heat.
Brush half the sauce over the pork and turn sweet potatoes. Rioast 5 minutes more until the sweet potatoes are tender and meast thermometer inserted in thickest part of pork registers 155 degrees F. (I find it takes my tenderloin closer to 20 minutes to reach that temperature).
Cut pork into 3/4 inch thick slices. Arrange on a platter with sweet potatoes. Pout any pan drippings and remaining sauce over the pork.
Makes 6 servings.
I like to double the amount of sauce. because my family loves it so much!