Slow Cooker Tacos

This looks really good and it's less than 450 calories for 2 tacos.  I would probably skip the cilantro for this altogether.  We could also go half ground beef and half turkey to dial back the calories a bit.  Looking forward to making this!

1lb lean ground beef
1 yellow onion, finely chopped
4 garlic cloves, chopped
1 16oz. can refried beans
1 16oz. jar salsa
1 C. shredded Cheddar cheese
2 serrano chiles, seeded
12 small corn tortillas
2 heirloom tomatoes, chopped
2 C. shredded lettuce
1/3 C. lowfat sour cream with a squirt of lime juice (I'd go with full fat sour cream; I don't like the lowfat)
Hot sauce to taste

In a large skillet over medium high heat, stir beef and onion until brown and cooked through, about 6 minutes.  Add garlic, stirring frequently for 1 minute.  Drain excess oils and transfer to a slow cooker.  Stir in beans, salsa, cheddar and serranos.  Cover and let simmer until mixture is cooked through and bubbling, 3 to 4 hours on high for 5 to 6 hours on low.  Stir and serve over warm tortilla; top with tomatoes, lettuce and a dollop of sour cream.  Garnish with cilantro.  Add hot sauce if desired.