01 - Preheat oven to 400°F. Rub potatoes with olive oil and sea salt, prick each several times with a fork, and place directly on oven rack. Bake 50-60 minutes until tender when pierced with a knife.
02 - While potatoes bake, heat 1 tablespoon olive oil in large skillet over medium-high heat. Add steak cubes and sear until browned on all sides, about 3-4 minutes. Remove steak and set aside.
03 - In same skillet, add diced onion and bell pepper. Sauté 3-4 minutes until softened. Add minced garlic, thyme, black pepper, and salt; cook 1 minute until fragrant. Return steak to pan, toss to combine, and remove from heat.
04 - Melt butter in small saucepan over medium heat. Whisk in flour and cook 1 minute to form roux.
05 - Gradually add milk and heavy cream to roux, whisking constantly until smooth and thickened, about 3-4 minutes. Reduce heat to low.
06 - Stir in grated Parmesan, nutmeg, salt, and white pepper until cheese melts and sauce becomes smooth. Remove from heat and keep warm.
07 - Once baked, let potatoes cool slightly. Slice each lengthwise and gently scoop out flesh, creating cavity (reserve scooped potato for another use).
08 - Fill each potato with steak and vegetable mixture. Drizzle generously with Parmesan cream sauce. Garnish with chopped chives and extra Parmesan if desired. Serve immediately.