1. In the bowl of a food processor, add the flours, sugar, and salt.
2. Scatter the butter pieces over the flour and pulse until you get a crumb-like consistency.
3. Add the ice water over, 1 tablespoon at a time, pulsing after each addition, until the dough will hold together when you pinch it together.
4. Dump the dough out onto a work surface, divide it roughly into 6 portions, and stretch each piece using the heel of your hand.
5. Scrape up the dough and gently shape it into a ball. Wrap it with plastic wrap, and chill for 30 minutes.
6. Remove the ball of dough from the fridge, cut into 4 pieces, stack them one on top of the other, gently press down and gather into a flat disc. Wrap again in plastic and chill for 30 more minutes.

For the filling:

1. In a large bowl add the sugar, cornstarch, lemon, and thyme and mix together. Add the Saskatoon berries and stir to combine.

Assemble:

1. Take the dough out of the refrigerator.
2. Dust a large piece of parchment paper with flour.
3. Using a rolling pin, roll out the dough in a circular shape to about ¼-inch (6 mm) thickness.
4. Gently place the parchment with the stretched dough onto a baking sheet.
5. In the meantime, preheat the oven to 400° F (200°C).
6. Pour the Saskatoon mixture onto the center of the crust, leaving some border around the edges.
7. Arrange the sliced peach in a circular manner over the Saskatoons and a couple of thyme sprigs on top.
8. Fold the edges of the crust over the berries toward the center.
9. In a little bowl whisk the egg yolk and water.
10. Brush the egg mixture over the crust edges and sprinkle organic cane sugar over the edges and on top.
11. Bake the galette for 20-25 minutes, or until the crust is golden and the fruit is bubbling.
12. Remove from the oven and let cool on a rack.