Flapjacks set in the tin before I cut them

The first tray of flapjacks I ever made came out of the oven smelling wonderful, and I cut it straight away because I could not wait. It fell apart into a warm, sticky heap of oats. We ate it with spoons and it was delicious, but it was not a flapjack. Since then I have one firm rule in my kitchen: flapjacks set in the tin before I cut them. The baking takes twenty-five minutes. The waiting takes longer, and the waiting is what makes them.

My flapjacks are the plain British kind, made from four things: butter, sugar, golden syrup and porridge oats. I use a 20 cm square tin, grease it and line it with baking paper that comes up over two sides like a sling, so the whole slab lifts out later. The oven goes on at 180°C (160°C fan, gas 4).

In a large saucepan on a low hob I melt 125 g of butter with 100 g of light brown soft sugar and 4 tablespoons of golden syrup. I dip the spoon in hot water first, so the syrup slides off instead of clinging. I stir gently until the butter has melted and the sugar has dissolved, and I do not let it boil hard. Hot syrup is a serious burn, so this is the part where I keep small hands away from the hob and turn the pan handle inwards. Then off the heat go 250 g of porridge oats and a pinch of salt, stirred until every oat is shiny and coated.

I tip the mixture into the tin and press it down firmly with the back of a spoon, right into the corners. Pressing matters as much as cooling: loose oats make crumbly flapjacks. They bake for 20 to 25 minutes, until golden at the edges and still a little soft in the middle. They look underdone when they come out. That is right. If you wait until the centre feels firm in the oven, they set like toffee and break your teeth.

Now the important part. While the slab is still warm, about ten minutes out of the oven, I score it into squares with a knife, pressing straight down, not sawing, but I do not take anything out. Then I leave the whole tin alone on the worktop until it is completely cold, at least an hour, and better two. As it cools, the butter and syrup firm up and glue the oats together. Only then do I lift the slab out by the paper and cut through the lines I scored earlier.

Done this way, every square comes away clean, chewy in the middle, a little crisp at the edges, with that deep golden syrup smell. They keep well in an airtight tin for several days, and they travel well in a lunch box or a coat pocket on a cold walk. Sometimes I stir in a handful of raisins or chopped dried apricots with the oats, but the method stays the same.

Flapjacks have no flour and no egg, but they are not free of allergens. Following the Food Standards Agency list of the 14 allergens, I note that they contain milk (butter) and oats, which are a cereal that can contain gluten, so anyone avoiding gluten needs oats labelled gluten-free. If I add dried fruit or nuts, I say so to whoever is eating them.

So my flapjack secret is not an ingredient at all. It is pressing the oats down firmly, taking the tray out while it still looks soft, and leaving it alone until it sets. Can you leave a warm tin on the worktop without cutting a corner?