Bring a large pot of salted water to a boil and cook pasta shells according to package directions until al dente. Drain and set aside.

Pat steak cubes dry with paper towels and season with salt and black pepper.

Heat olive oil in a large skillet over high heat until shimmering.

Add steak bites in a single layer and sear for 2 minutes per side until a brown crust forms. Work in batches if necessary to avoid crowding.

Reduce skillet heat to medium. Add 4 tbsp butter, minced garlic, and dried thyme. Toss steak bites for 1 minute to coat in the garlic butter, then remove steak from the pan and set aside.

In a separate saucepan, combine heavy cream and 0.5 cup butter over medium heat until simmering.

Whisk in shredded cheddar cheese, parmesan cheese, and garlic powder. Stir constantly until the sauce is smooth and thickened.

Fold the cooked pasta shells into the cheddar alfredo sauce until evenly coated.

Divide the cheesy shells into bowls and top with the garlic butter steak bites.

Garnish with cooked bacon bits and chopped chives before serving.