Preheat the oven to 375 degrees. Line a baking sheet with parchment paper.
Place the peach slices and blueberries into a bowl and sprinkle them with the lemon juice then gently toss to coat with the juice.
Add the sugar, cornstarch and cinnamon to the peaches and blueberries then toss to coat evenly.
Place the peach slices in a spiral inside the pie crust starting one inch from the edge. Sprinkle the top with the blueberries.
Fold the edge of the dough over the fruit.
Brush the dough with the beaten egg. Sprinkle the edges with the sliced almonds and a bit of turbinado sugar.
Add the diced butter to the top of the fruit.
Place into the oven and bake for 40-45 minutes, or until golden brown.
Remove the galette from the oven and let cool for 10-15 minutes before slicing.
Serve with vanilla ice cream or whipped cream, if desired. Enjoy.