Turn the oven onto 350 degrees.
Make the Filling.
Add 3 cups frozen raspberries to a mixing bowl.
Add in honey (or sugar) and arrowroot powder, mixing gently.
Make the Sourdough Raspberry Galette:
Roll out the crust to about 13 inches around. It does not have to be a perfect circle.
Pour the filling onto the crust, leaving about 3 inches of the crust.
Fold the ends over to create this beautiful crust around the galette. Take your time with this.
Line a baking sheet with parchment paper and gently set the galette onto it.
Brush the crust with the milk and top with sprinkle with a little sugar.
Place in the oven for 35-40 minutes.
Enjoy!