Galette with apples and walnuts

Ingredients:

Dough

• 1 and 1/4 cups premium flour + extra for dusting
• 2 tsp. granulated sugar
• A pinch of salt
• 110g chilled unsalted butter, cut into 1cm pieces.
• 1 large egg

Filling

• 1 cup walnuts
• 1/4 cup + 1 tbsp granulated sugar
• 1 large egg
• 3 tablespoons unsalted butter, diced
• 1/4 tsp vanilla extract
• A pinch of salt
• 3 Golden Delicious apples or other firm baking apples (about 600 g)
• 1/4 cup apricot jam
• Powdered sugar, for dusting (optional)

Preparation:

1. Position racks in the middle and lower thirds of the oven; preheat oven to 350°F (175°C).
2. Knead the dough:
   
   Combine the flour, sugar, and salt in a food processor until evenly distributed. Add the butter; pulse until the mixture resembles coarse meal with pea-sized pieces of butter. Whisk the egg in a bowl with 1 tablespoon of ice water, then add it to the food processor and pulse once or twice. Stop until the dough forms a ball.
3. Place it on a piece of cling film and form it into a disk. Wrap tightly and refrigerate for 1 hour.
4. Meanwhile, prepare the filling.:
   
   Toast the walnuts on a baking sheet on the middle rack of the oven until golden brown, 7-8 minutes; let cool. In a clean food processor, pulse the walnuts, 1/4 cup granulated sugar, egg, 1 tablespoon butter, vanilla extract, and salt to form a paste.
5. Line a flat baking sheet (or an inverted baking sheet) with parchment paper. On a floured work surface, roll out the dough into a 30 cm diameter circle. Place the dough on a rolling pin, then transfer it to the parchment.
6. Spread the walnut filling over the dough, leaving a 4 cm border around the edges. Refrigerate while you prepare the apples.
7. Increase the oven temperature to 200°C. Peel, core, and cut the apples in half, then cut each half into 8 wedges.
8. Arrange the apple slices in a circle over the filling, slightly overlapping them. Fold the edges of the dough over the filling. Sprinkle the apples with the remaining 1 tablespoon of sugar and 2 tablespoons of butter.
9. Bake the galette on the middle rack of the oven until golden brown, 40-45 minutes. Place the baking sheet on the bottom rack to catch the juices. Cool the galette on the rack.
10. In a bowl, combine 1 tablespoon of water with the apricot jam. Strain the glaze, then brush it over the apples. Dust with powdered sugar, if desired.