01 -
In a food processor, combine all-purpose flour, granulated sugar, salt, and cold unsalted butter. Pulse for approximately 1 minute, until the mixture forms pea-sized pieces. Gradually add ice water, one tablespoon at a time, pulsing just until the dough holds together.
02 -
Transfer dough to a lightly floured surface. Form into a disk, wrap tightly in plastic, and chill in the refrigerator for at least 1 hour.
03 -
In a bowl, thoroughly combine rhubarb, strawberries, light brown sugar, lemon juice, lemon zest, corn starch, and vanilla seeds.
04 -
Roll the chilled dough on a lightly floured surface to form a rough circle, about 0.5 cm thick. Carefully transfer to a baking sheet lined with parchment paper.
05 -
Sprinkle instant oats evenly over the dough, then pile the fruit mixture in the center, leaving a border of 4 cm. Fold the edges of the dough up and over the fruit, overlapping slightly for a rustic look.
06 -
Transfer the baking sheet with the formed galette to the freezer and chill for 15 minutes to set the shape.
07 -
While the galette chills, preheat oven to 190°C.
08 -
Remove the galette from the freezer. Brush the crust with beaten egg and milk mixture, then sprinkle generously with coarse sugar.
09 -
Bake in the preheated oven until the crust is deeply golden and the filling is bubbling, about 40–45 minutes.
10 -
Allow to cool briefly. Slice and serve warm with a scoop of vanilla ice cream.