Preheat your oven to 375°F (190°C).

In a large, heavy-bottomed pot, heat 2 tablespoons of butter and 1 tablespoon of olive oil over medium-high heat. Season the top sirloin cubes with salt and pepper, then brown in the pot for about 6–8 minutes.

Add 1 chopped onion and 2–3 diced carrots to the pot and cook for 4–5 minutes.

Sprinkle 2 tablespoons of flour over the beef and vegetable mixture, stirring continuously for 1-2 minutes to avoid lumps.

Pour in 2 cups of apple cider and 2 cups of beef broth, stir to combine, bring to a boil, then reduce heat and let simmer.

Transfer the mixture to an oven-safe dish, cover, and bake for 1 to 1.5 hours.

Boil a large pot of salted water, add peeled and diced potatoes and cook until fork-tender (15–20 minutes).

Drain the potatoes, return them to the pot, and add 1/4 cup of milk, 1/2 cup of sour cream, and 1/2 cup of shredded cheddar cheese; mash until smooth.

Serve the hearty beef stew over the creamy mashed potatoes, garnished with chopped chives.