One of the challenges of making things from scratch is that you occasionally make more than you know what to do with.

A little while ago I found myself with a substantial quantity of roasted tomato passata sitting in the refrigerator. The passata itself had come from an excess of tomatoes that had been roasted to concentrate their flavour before being blended and strained. The result was far richer and sweeter than anything that comes from a supermarket bottle, but there was only so much pasta sauce a person could eat.

After a week or two of staring at a litre and a half of passata every time I opened the fridge, it became obvious that something had to be done. It was still perfectly good, but it certainly wasn’t going to last forever.

The answer was to turn it into a tomato sauce.

Before any cooking began, I assembled the ingredients on the bench: onions, garlic, vinegar, brown sugar and a handful of spices, including smoked paprika and a little chilli. It was a simple collection of ingredients, but together they would transform the passata into something quite different.

The passata went into a large pot and simmered slowly while the flavours melded together and the sauce thickened. One of the pleasures of cooking with roasted tomatoes is that much of the work has already been done. The roasting process develops sweetness and depth that simply isn’t present in raw tomatoes. The finished sauce retained that rich tomato flavour while gaining the tang and spice that makes a good condiment.

By the end of the afternoon, the litre and a half of passata had become two 600-millilitre jars of tomato sauce, along with a smaller half-litre bottle that went straight into the refrigerator for immediate use. It always amazes me how much volume disappears during cooking, but what is lost in quantity is usually gained in flavour.

The two larger jars were preserved using the boiling-water canning method. Once sealed and cooled they joined the pantry, ready for a pie, sausage roll, burger or whatever else might benefit from a spoonful of tomato sauce. The half-litre bottle in the fridge, however, won’t be there for long.

There is something deeply satisfying about taking a surplus ingredient that might otherwise go to waste and turning it into something with a much longer future. In this case, a litre and a half of roasted tomato passata became two jars for the pantry and one bottle for the fridge, extending the life of the tomatoes by many months and ensuring that none of the effort that went into growing, roasting and processing them was wasted.

Food preservation is often seen as a practical necessity, but I think it is also an act of optimism. You spend a day in the kitchen today because you know there will come a day in the future when opening a jar of homemade tomato sauce will be exactly the right thing.