In a large skillet, heat olive oil over medium-high heat. Sear the flank steak pieces until browned on all sides (about 3-4 minutes). Remove from heat.
Place the diced potatoes at the bottom of the slow cooker. Add the seared steak on top of the potatoes.
In a mixing bowl, combine the chopped onion, minced garlic, beef broth, pepper, smoked paprika, and salt. Pour this mixture over the steak and potatoes in the slow cooker.
Cover and cook on low for 6-8 hours or on high for 3-4 hours, until the steak and potatoes are tender.
Once cooking time is complete, stir in the shredded cheddar cheese and sour cream until well combined and melted.
Allow the mixture to cook for an additional 10-15 minutes on low, allowing the cheese to fully melt and flavors to meld.
Before serving, garnish with sliced green onions for a fresh touch.
Notes
For a spicier kick, consider adding jalapeños or hot sauce.