For the dough:
For the blueberry buttercream:
For the dough, mix the plant-based milk and yeast and let it rest for a few minutes.
Then add the rest of the dough ingredients and incorporate. Knead for about 15 minutes until the dough becomes stretchy and let it rise for 2 hours.
Mix all the ingredients for the buttercream in a bowl using an electric mixer and beat at high speed until the blueberries are mashed and everything is soft.
Pour the buttercream into an about 10×10-inch rectangular bag and freeze.
To assemble the croissants, roll out the dough until covering the frozen buttercream block. Put the block in the center and wrap it in the dough.
Use a rolling pin to extend the dough until the length is 3 times the width, and fold in three as if it were a leaflet. Refrigerate for 1 hour and repeat this process 5 times.
Preheat the oven to 400°F.
Once the folding is done, cut triangles of 10 inches in height and a base of 4 inches. Put two blackberries on the base and roll up.
Place the croissants in an oven tray and bake for 15 minutes.
Sprinkle some powdered sugar on top before serving.