Gâteau Basque Loaf
Makes 1 (9x5-inch) cake
  • ¾ cup (170 grams) unsalted butter, softened
  • 1⅔ cups (333 grams) granulated sugar
  • 3 large eggs (150 grams), divided
  • 2 large egg yolks (37 grams)
  • 3¼ cups (406 grams) all-purpose flour
  • 2¼ teaspoons (11 grams) baking powder
  • 1¼ teaspoons (3.75 grams) kosher salt
  • Custard Filling (recipe follows)
  • ¾ cup (128 grams) fresh blueberries
  • 1 tablespoon (15 grams) water
  • Garnish: confectioners’ sugar
  1. In the bowl of a stand mixer fitted with the paddle attachment, beat butter and granulated sugar at medium speed until fluffy, 3 to 4 minutes, stopping to scrape sides of bowl. Add 2 eggs (100 grams) and egg yolks, one at a time, beating well after each addition.
  2. In a medium bowl, whisk together flour, baking powder, and salt. With mixer on low speed, gradually add flour mixture to butter mixture, beating just until combined. Turn out dough, and shape into a disk. Wrap in plastic wrap, and refrigerate until firm, about 2 hours or up to overnight.
  3. Line a 9x5-inch loaf pan with parchment paper, letting excess extend over sides of pan.
  4. On a heavily floured surface, roll dough to ¼-inch thickness. Cut a 9-inch square from dough. Gently transfer to prepared pan, placing in bottom and up sides. Cut 2 (4½x3-inch) rectangles from dough, and place widthwise on either ends of prepared pan. Press dough together in corners to seal. (See Note.)
  5. Reroll remaining dough to ¼-inch thickness, and cut a 9x5-inch rectangle from dough. Transfer to a sheet of parchment paper, and refrigerate.
  6. In bottom of pan, place blueberries in a single layer. Spoon Custard Filling on top of blueberries, smoothing flat, and tap pan on counter 3 times to release air bubbles. Trim dough to ⅛ inch above Custard Filling.
  7. In a small bowl, whisk together 1 tablespoon (15 grams) water and remaining 1 egg (50 grams). Brush top of dough in pan with egg wash. Place 9x5-inch dough rectangle on top, pressing around edges to seal. Freeze until set, 30 to 45 minutes.
  8. Preheat oven to 400°F (200°C).
  9. Brush dough with egg wash.
  10. Bake for 20 minutes. Reduce oven temperature to 350°F (180°C), and bake until top is deep golden brown and a wooden pick inserted in top (but not in custard) comes out clean, about 40 minutes more, covering with foil after 20 minutes of baking to prevent excess browning. Let cool in pan for 15 minutes. Using excess parchment as handles, remove from pan, and let cool completely on a wire rack. Just before serving, garnish with confectioners’ sugar, if desired. Refrigerate in an airtight container for up to 4 days.
Note: This dough is very forgiving. Reroll when needed, and if it tears, just press it back together. If the dough gets too soft while working with it, refrigerate it for a few minutes. If you refrigerate the dough overnight, let it stand for 5 to 10 minutes before rolling it out.
Recipe by Bake from Scratch at https://www.bakefromscratch.com/gateau-basque-loaf/