Step 1: Season the steak cubes generously with salt and pepper. Heat olive oil in a large Dutch oven over medium-high heat. Sear the steak in batches until browned on all sides. Remove the steak and set aside.
Step 2: In the same pot, melt the butter. Add the onion, carrots, and celery. Sauté for 5-7 minutes until the vegetables begin to soften.
Step 3: Add the minced garlic, thyme, and rosemary. Cook for another 1 minute until fragrant. Sprinkle the flour over the vegetables and stir constantly for 2 minutes to cook out the raw flour taste.
Step 4: Slowly pour in the beef broth while whisking or stirring constantly to prevent lumps. Bring the mixture to a gentle boil.
Step 5: Add the diced potatoes to the pot. Reduce heat to low, cover, and simmer for 15-20 minutes, or until the potatoes are fork-tender.
Step 6: Stir in the heavy cream and return the seared steak (along with any juices) to the pot. Simmer for an additional 5 minutes to heat through. Adjust seasoning with salt and pepper. Garnish with fresh chives before serving.