Preheat your oven to 375°F (190°C). In a large skillet, heat 2 tablespoons of olive oil and 1 tablespoon of butter over medium-high heat. Season the top sirloin cubes with salt and pepper, then sear them until browned on all sides, about 6-8 minutes.

Add 1 diced onion and 2 chopped carrots to the skillet with the beef, stirring occasionally. Sauté for 4-5 minutes until the onion becomes translucent.

Sprinkle 2 tablespoons of flour over the beef and vegetables, stirring to coat evenly. Slowly pour in 2 cups of apple cider and 1 cup of beef broth, stirring until the mixture comes to a boil.

Transfer the mixture to a Dutch oven, cover it tightly, and bake in the preheated oven for 60-90 minutes.

While the stew is baking, peel and chop 2 pounds of potatoes. In a pot, bring water to a boil, add the potatoes, and cook until tender, about 20-25 minutes.

Drain the cooked potatoes, then mash them with 1/2 cup of milk, 1/2 cup of sour cream, and 1 cup of shredded cheddar cheese until creamy.

On a warm plate, spoon a generous amount of creamy cheddar mashed potatoes. Top with the hearty apple cider beef stew and garnish with fresh chives.