Combine frozen blueberries and sugar in a saucepan over medium heat.

Cook until the mixture thickens and reduces, then cool to room temperature.

Sift cake flour and almond flour for the crumble.

Mix flour and sugar, then add cold diced butter.

Use a scraper to mix butter into the dry ingredients, then rub with hands until crumbly.

Cream softened butter for cookie dough, then mix in sugar.

Add egg yolk and mix thoroughly.

Fold in cake flour and almond flour until combined.

Wrap dough and refrigerate for 30 minutes.

Roll dough into a 20cm square and place in a lined baking pan.

Poke holes in the dough with a fork to prevent puffing.

Spread blueberry jam evenly over the dough.

Sprinkle crumble evenly over the jam.

Bake at 170°C for 25–30 minutes until golden brown.

Cool completely before removing from the pan.