In a medium sized saute pan, fry off your lardons over a medium heat until crisp. Remove your lardons from the pan with a slotted spoon, leaving your fat in the pan. Set your lardons aside.
Add your onion and carrot to the pan and cook over a low-medium heat for 15 mins until soft and starting to caramelise. Add your seasoning and cook out for 2 mins.
Add your tomatoes to the pan and break up with the back of your spoon. Fill your can with water and add this to the pan to release any tomato residue on the sides. Bring to a boil, then simmer for 20 mins until thick and jammy.
Add your lardons back to the pan along with your baked beans and reduce for 5 mins until you have a thick sauce. Season to taste, then leave to cool.
Heat your oven to 190°C.
Cut your pastry into large discs and cut incisions in one half. Spoon your mixture onto the opposite half of your pastry, then wet the edges with a little water and fold over. Seal the edges with a fork. Brush with a little oil mixed with your sauce, then repeat with your remaining pastry and filling.
Place on a preheated baking tray and cook for 15-20 mins until golden and crisp.