Boil Pasta: In a large pot, boil spaghetti noodles to al dente, according to package directions.
Cook Onion: In a large skillet over medium-high heat, add olive oil. When oil is hot, add onion and cook 2-3 minutes until soft.
Brown Ground Beef: Add ground beef and season with taco seasoning. Cook beef 2-3 minutes (until browned), breaking the meat up as it cooks. Pro Tip: Using a potato masher when the meat is about halfway cooked works great at getting the meat broken up nice and fine :)
Add & Simmer: To the "taco meat", add tomato sauce, diced green chilis, chipotle chilis + adobo sauce, sugar and oregano. Stir to combine. Bring sauce to a boil, then turn the heat down to medium-low and simmer sauce 5-10 minutes until all flavors are combined.
Add Sour Cream: Turn heat down to LOW and stir in sour cream (make sure the heat is LOW otherwise the sour cream has a tendency to separate).
Finish: Last, add your cooked pasta and half of the shredded cheese (save the other half for sprinkling on top!). With tongs, toss everything until spaghetti is well combined with the sauce and cheese is melted.
Serve immediately and top with remaining cheese + green onions/cilantro/sliced black olives if you like!