Preheat oven to 350 degrees
Heat oil in medium-sized skillet over medium heat. Add onions and mushrooms, stir to coat them with oil. Cook for 10 minutes, stirring occasionally until the mushrooms are tender and the onion starts to caramelize. Stir in the garlic and cook for 1 more minute.
Add bacon and ground beef to the skillet crumbling it as it cooks. Continue cooking until the beef is no longer pink. Add wine, worcestershire sauce, tomato sauce and pepper to the beef mixture. Simmer until the liquid starts to cook down and the mixture is slightly thickened. Remove from heat.
Cook cauliflower according to package directions. Drain the excess liquid. Place cauliflower in a food processor or high speed blender. Add butter and cream and pulse until the mixture is smooth and creamy. Season to taste with salt and pepper.
Spread mashed cauliflower evenly over beef mixture and top with cheese. Bake for 20-25 minutes, or until heated through and the cheese is melted. Garnish with chives and enjoy!