Instructions

1. For the crust, combine flour, salt, and sugar in a food processor. Add cubed butter and process for 10 seconds, just until the mixture resembles coarse meal. With the food processor running, add 2 tablespoons ice water in a steady stream through feed tube. If needed, add additional ice water 1 tablespoon at a time, and process just until dough holds together in large clumps (no more than 30 seconds). Wrap dough in plastic and flatten slightly to form a disc. Chill in the refrigerator at least 1 hour (or up to 2 days, or place in a freezer bag and freeze up to 1 month).
2. For the topping, combine flour, sugar, and salt in a medium bowl. Cut in butter with a pastry cutter until completely incorporated and large crumbs form; fold in sliced almonds. Chill until ready to use.
3. Line a baking sheet with parchment paper. Place dough on a floured board and dust dough with flour. Roll out dough (roll dough in one direction, then lift up dough and rotate a quarter turn and roll, then repeat) until dough is a 12-inch circle. If dough starts to stick, use a bench scraper to lift dough from board. Transfer dough to prepared baking sheet and chill in the refrigerator for 15 minutes. Preheat oven to 400°F.
4. For the filling, place 1/2 cup blueberries in a large bowl and crush gently with a fork. Add remaining blueberries, sugar, cornstarch, salt, and lemon juice and toss to combine.
5. Spoon filling over chilled crust, leaving a 2-inch border. Sprinkle evenly with crumb topping and fold up the pastry border, pressing the edges with a fork to seal. Chill assembled galette for 15 minutes.
6. Brush pastry with milk and sprinkle with sugar. Bake galette for 25 minutes, then tent with aluminum foil to prevent over-browning. Continue baking another 10 to 15 minutes (for a total baking time of 35 to 40 minutes), or until pastry is golden and filling is bubbly. Let cool for 1 hour on a wire rack before cutting and serving.