Make the dough

• Mix the flour, sugar and salt in a bowl, then rub in the cold butter until crumbly.
• Add the cold water and bring together into a dough without overworking it.
• Divide the dough in half, flatten into discs and chill in the fridge.

Cook the blueberry lemon filling

• Combine the blueberries, honey, lemon juice, lemon zest and cornstarch in a saucepan.
• Simmer, stirring, until the berries burst and the filling thickens.
• Let cool completely.

Roll and cut the pastry

• Roll each half of the dough into a large rectangle on a floured surface.
• Cut each rectangle into 8 smaller rectangles, for 16 in total.

Fill and seal the tarts

• Spoon the blueberry filling onto half of the rectangles.
• Brush the edges with egg wash and top with the remaining rectangles, pressing to seal.
• Poke a few holes in the top of each tart to let steam escape.

Bake

• Bake the tarts until the pastry is golden brown and crisp.

Ice and decorate

• Whisk the powdered sugar with some of the leftover blueberry filling to make a naturally colored icing.
• Spread the icing over the cooled tarts and top with crushed sprinkles.