Blueberry-Poppy Seed Squares (Borůvkový Koláč)

The floral character of poppy seeds shines when paired with blueberries in this rich dessert. Store any unused seeds in the refrigerator or freezer.

Blueberry-Poppy Seed Squares (Borůvkový Koláč) Blueberry-Poppy Seed Squares (Borůvkový Koláč)
The floral character of poppy seeds shines when paired with blueberries in this rich dessert.
Yield: serves 12

Ingredients

  • 20 tbsp. unsalted butter, softened, plus more for pan
  • 3 cups flour, plus more for pan
  • 1 12 cups sugar
  • 34 tsp. kosher salt
  • 14 tsp. vanilla
  • 4 cups blueberries
  • 2 tbsp. fresh lemon juice
  • 12 tsp. ground cinnamon
  • 1 12 cups ground poppy seeds (available at Kalustyan’s)
  • 12 cup heavy cream

Instructions

  1. Heat oven to 350°. Butter and flour a 9″ x 13″ metal baking pan; set aside. Beat 16 tbsp. butter and 12 cup sugar on medium-high speed of a mixer until pale and fluffy, about 2 minutes. Add 2 12 cups flour and 12 tsp. salt; beat until just combined. Press dough into bottom and halfway up sides of prepared pan; chill for 20 minutes. Bake crust until lightly browned, about 12 minutes; let cool. Meanwhile, stir remaining butter, flour, and salt, 14 cup sugar, and vanilla in a bowl until coarse crumbles form; set streusel aside.
  2. Heat remaining sugar, 3 cups blueberries, lemon juice, and cinnamon in a 2-qt. saucepan over medium-high heat; cook until berries burst, about 20 minutes. Remove from heat and stir in remaining berries; let cool. Stir together poppy seeds and cream in a bowl; spread evenly over cooled crust. Pour blueberry mixture over poppy seeds; sprinkle with streusel mixture. Bake until filling is bubbly and streusel is lightly browned, about 40 minutes. Let cool, cut into squares, and serve.