Preheat your oven to 350°F. In a mixing bowl, add together the almond flour, sugar, and a pinch of salt. Incorporate the melted butter and mix well.
Add in the egg and mix until the dough comes together. It should create a ball of dough.
Line a baking tray with parchment paper. Place the dough on top, then layer another parchment paper on top. Then you can easily roll the dough to be about 1 cm thick. Gently remove the top parchment layer.
Add the sliced peaches and blueberries on top of the rolled dough, leaving about 1 inch of space on the edges to fold over.
With your fingers, gently lift the free 1 inch space of dough and fold over to create a border around the galette. The almond flour dough will be more crumbly than normal dough, this is normal. Gently press together edges and areas that start to crumble or separate.
In a small separate bowl, create the topping crumble. Add the cold butter, brown sugar, almond flour, cinnamon, and coarsely chopped walnuts into the bowl. Then using your fingers or a fork, mix together until it begins to resemble clumps of sand.
Sprinkle the crumble topping on top of the peaches and blueberries. Try to separate the clumps to cover about 40% of the top layer.
Bake for 20 minutes or until the crust is golden brown. Then remove from oven.
While still warm, cut even slices and top with ice cream. Serve fresh!