How to Make It
Preheat broiler with oven rack 6 inches from heat. Heat oil in a large skillet over medium-high. Add onion, garlic, and 1 teaspoon salt. Cook, stirring often, until onion begins to brown, about 10 minutes. Stir in vinegar, and cook 1 minute. Add 2 cups cheese, sour cream, and 1/2 cup Hatch chile salsa, and stir until smooth. Fold in pork, and cook, stirring occasionally, until mixture is hot but not bubbling.
Spoon about 1/3 cup pork mixture down middle of each tortilla, and roll up. Place seam side down in a lightly greased 13- x 9-inch broiler-safe baking dish. Pour remaining 1 cup Hatch chile salsa over tortillas; sprinkle with remaining 1 cup cheese. Broil in preheated oven until cheese is melted and browned in places, about 3 minutes. Let stand 5 minutes.
While enchiladas stand, stir together avocado, cilantro, pepitas, olive oil, lime juice, and remaining 1/4 teaspoon salt in a small bowl. Spoon over enchiladas, and serve with additional sour cream.