Use a whisk to cream the butter and sugar until you have an even texture.

Add the salt, vanilla essence and mix again.

Finish by adding the flour and mixing it in using a spatula. Only mix it by hand slightly if it needs further incorporating. Keep it to a minimum dough as it gets tough if over-kneaded.

Cut baking paper so it fits into the mould. It should cover the base of the mould and have extra pieces at each side to cover them for an easy unmoulding afterwards. You can stick the paper to the mould using a bit of vegetable oil and spreading it using a piece of kitchen paper.

Spread out the dough on the base of the mould by pressing down with your fingers. Try to make it as even as posible.

Cook the dough in a preheated oven at 180C / 350F for 15-25min or until golden.

Let it cool down completely before spreading the berries on top or it will absorb their juices and become soggy.

If the berries are frozen let them thaw completely on a colander and discard the liquid they release in this process. You want to measure the berries at this point.

If some berries are a bit big you can cut them in half or quarters.

Mix the berries with the rest of the filling’s ingredients and spread them onto the base we baked previously.

Place all the ingredients in a bowl and use your fingers to pinch the butter with the rest of the ingredients. You can also do this on a food processor.

Stop pinching the butter when there’s no butter pieces and the mix looks like wet sand.

Sprinkle the crumble over the berries using your fingers to separate the crumbles as they fall.

Cook the berry bars in a preheated oven at 180C /350F for 30-35min. If the crumble is sufficiently golden before this you can cover the mould with tin foil to prevent it from burning. Don’t remove it from the oven before that time, the flour in the filling needs at least this much to cook.

Let it cool completely before unmoulding. Lift the bars by lifting it from the sides of the paper and cut them is squares.