Put rinsed berries and sugar into a saucepan and stir to combine.

Heat on medium to medium high (stirring almost constantly) until the berries start to break down and release their juice.

When the mixture comes to a boil, lower the heat and simmer until the berries have broken down almost completely into a saucy consistency.

Make a slurry of the cornstarch and a little water, mixing until smooth, and stir it into the sauce.

Bring back to the boil and cook gently for a minute or two more, until the sauce has thickened.

Let cool to room temperature before using.

Preheat oven to 350F. Lightly spray a 9x13 baking pan.

Put the flours, sugar, baking powder and salt in a food processor and pulse to combine.

Add the cold butter (cut in pieces), egg, and almond extract to the bowl. Pulse until the mixture becomes crumbly.

Put ⅔ of the dough in the bottom of the prepared pan and smooth it.

Spread a thick layer of jam over the top of the crust.

Sprinkle the rest of the dough over the jam, followed by the sliced almonds.

Sprinkle 1 teaspoon sugar evenly over the top. Bake for 30 minutes, or until just starting to turn golden around the edges.