Preheat the oven to 180°C / 350°F.

Place 250 g all-purpose flour, 36 g light brown sugar, and 0.5 g fleur de sel in a mixing bowl.

Rub 100 g butter into the dry ingredients with your fingertips, leaving small butter pieces.

Add up to 50 ml cold water gradually and gather the mixture into a dough ball.

Set the dough aside while preparing the fruit.

Cut 6 yellow nectarines into wedges, discarding the stones.

Combine the nectarine wedges with 12 g brown sugar and 7.5 g vanilla sugar in a mixing bowl.

Add 8 g cornstarch and toss the fruit until evenly coated.

Roll the dough into a rough circle on the work surface.

Transfer the dough circle to a baking sheet lined with parchment paper.

Crush 40 g speculoos biscuit with the rolling pin and scatter the crumbs over the dough center.

Arrange the coated nectarines over the biscuit crumbs, leaving a wide dough border.

Fold the exposed dough border up and over the outer edge of the fruit.

Bake the galette at 180°C / 350°F for 40 min until the crust is golden and the fruit is bubbling.