Preheat oven to 400°F.
Cut the cauliflower head vertically into about 1 inch thick planks. Don't worry if some planks fall apart. Set aside.
Over medium-high, heat a splash of olive oil in a pan. Add shallots and garlic and cook, stirring occasionally, until fragrant, about 1-2 minutes. Add chopped Roma tomatoes and season with salt and pepper to taste. Sauté until tomatoes start to soften, about 3-4 minutes, stirring often. Add tomato paste and chicken stock. Reduce the heat to medium-low and let simmer until liquid reduces in half, about 4-5 minutes. Add half the chopped basil and mix well. Remove from heat and set aside.
Lay out sliced cauliflower onto a sheet pan. Spread the tomato sauce evenly onto the cauliflower. Place sliced mozzarella on top and sprinkle generously with grated parmesan. Transfer to the oven and roast for about 20-25 minutes, until the cauliflower softens and cheese starts to brown on the sides.
Remove from the oven. Serve the cauliflower with some freshly grated parmesan and remaining chopped basil. Enjoy!
