For the sauce, peel and finely dice the onion. Heat the rapeseed oil in a saucepan. Add the onion cubes and sauté lightly. Add the strained tomatoes, vinegar, Worcester sauce, espresso, tomato paste, sugar, smoked salt, mustard flour, cumin powder, mild and smoked paprika powder, some black pepper from the mill and some grated lemon peel and bring to the boil. Then add the cola and bring to the boil again.
For the hot version, add the chilli flakes and the hot, smoked paprika powder.
Finally, with both variations, stir in the whiskey and maple syrup, reduce the temperature to the lowest possible flame and let the liquid simmer to add to the sauce.