Have Ready - tortillas, warmed ovenproof casserole dish, grated cheese, and chopped white onion.
Prepare Swiss Chard - Wash carefully. Divide chard between 2 plastic freezer bags, add ¼ cup water to each and seal. Cook on high in Microwave for 5 minutes. Remove and drain. Chop chard into small bits by hand. Heat 3 tbsp oil in fa skillet over medium heat and fry garlic for 2 minutes. Add the chard and cook for another 3 minutes. Adjust salt and remove to a bowl. Rinse out skillet.
Prepare Tomato Sauce - Blend tomatoes, 1 clove garlic, ¼ onion, 2 chipotles until smooth. In rinsed frying pan, heat 2 tbsp oil over medium-high heat. Add tomato sauce, ¼ tsp sugar, and salt. Cook, constantly stirring, until reduced - about 5 minutes. Add in broth, bring to a boil then remove from heat and cover.
Warm Tortillas - Fill a low-sided nonstick frying pan with ¼-inch oil. Heat over medium high heat. When hot, fry tortillas one-by-one. Fry around 20-30 seconds per side. Drain on paper towels and keep warm.
Assemble Enchiladas - Preheat broiler. Pour tomato sauce into the nonstick pan. Immerse a tortilla in the sauce and gently remove to the casserole, Add some filling and a little sour cream, Roll it up into a flat cylinder. Repeat aligning completed enchiladas side-by-side in the dish. Dilute any remaining sauce, if any, with a little broth and pour over enchiladas.
Finish and Serve - Sprinkle cheese over enchiladas. Run under the broiler to melt cheese. Sprinkle tops with chopped onions and serve.