In a heated medium-sized pan, drizzle some olive oil, add onion, bell peppers, Italian herbs, garlic and cook till soft. Add spinach to pan and stir till the spinach has wilted, season with salt and pepper and keep aside.

Heat a medium-sized pot over medium heat then add butter, as soon as it melts add the flour and stir around for a minute. Add warm milk gradually and whisk continuously making sure no lumps are formed. Cook for about 3 minutes on a low fame and turn off. Let it sit for a minute then add the grated parmesan and whisk till all the cheese has melted, place aside for use later.

Preheat oven to 180°C. Line a large baking tray with parchment paper. Place the pizza base on the tray.

Spoon out the white sauce and spread evenly to the sides. Sprinkle some of the grated mozzarella and cheddar cheese. Place 2-3 slices of the ham, and some more cheese. Spoon out the sautéed spinach and peppers evenly. Season with salt and pepper. Spoon out a few dollops of the tomato sauce around and another layer of grated mozzarella and cheddar cheese.

Roll the Pizza base with the toppings lengthwise like a jelly roll. Brush the entire Stromboli with tomato sauce and more cheese on top. Bake for 15-25 mins at 180°C or until golden brown. Let cool for 5 mins before slicing. Serve with extra tomato sauce, if desired.