In large skillet, heat oil to medium high heat.
Combine chili powder, cumin and smoked paprika in small bowl, then rub into beef.
Put beef in the skillet once oil is hot and sear each side.
Once the beef has been seared, return to slow cooker.
Add beef broth, tomato paste, and minced chipotle to skillet, being sure to scrape up the browned bits from around the pan.
Bring sauce to boil and reduce heat - then simmer for a few minutes until the sauce has thickened a bit.
Add diced onion and garlic on top of the beef in the slow cooker. Then pour sauce over top of the beef, onions and garlic.
Cook on low 6-8 hours.
Remove beef from slow cooker and shred with two forks. Mix in onions with beef.
Serve on top of tortillas and add your favorite toppings - enjoy!