1. In a large bowl, combine flour, sugar, and salt. Add cold, cubed butter and work it into the flour mixture until it resembles coarse crumbs. Gradually add ice water until the dough comes together. Wrap it in plastic wrap and chill for at least 30 minutes.

2. Slice strawberries and peaches, then toss them in a bowl with sugar, lemon juice, and vanilla extract. Let the mixture sit for a few minutes.

3. Roll out the chilled dough on a floured surface into a rough circle. Transfer it to a baking sheet lined with parchment paper. Spoon the fruit filling onto the center of the dough, leaving a border around the edges. Fold the edges over the filling, pleating as you go. Brush the crust with an egg wash.

4. Preheat oven to 375°F (190°C) and bake the galette for about 40-45 minutes, or until the crust is golden brown and the fruit is bubbling. Let it cool slightly before serving.