Heat 2 tablespoons of olive oil in a large skillet over medium-high heat. Once shimmering, add the thinly sliced beef sirloin in a single layer and allow it to sear without moving for 3-4 minutes until browned. Remove the beef from the skillet and set aside.

In the same skillet, toss in the diced green bell pepper, sliced onion, and baby bella mushrooms. Sauté for 5-7 minutes until tender and slightly caramelized, stirring occasionally. In the last minute of cooking, add minced garlic and stir until aromatic.

Melt 1 tablespoon of butter in a separate pan over medium heat. Add the riced cauliflower and sauté for 5-7 minutes, stirring frequently until golden and tender. Season with salt and pepper.

Return the cooked beef to the skillet with the vegetables. Pour Worcestershire sauce over and stir well. Cook for an additional minute, then sprinkle provolone cheese over the top. Cover the skillet for 1-2 minutes until the cheese melts.

Divide the seasoned riced cauliflower among serving bowls. Heap the beef and vegetable mixture topped with melted cheese on each bowl. Garnish with chopped parsley.