hazelnut plum crumb tart

INGREDIENTS

• 1/2 cup granulated sugar
• 3/4 cup unsalted butter (1 1/2 sticks), chilled, cut into small pieces, plus more for pan
• 1/3 cup (1 3/4 ounces of 49 grams) hazelnuts
• 1 1/2 cups (188 grams) all-purpose flour
• 1/3 cup packed light or dark brown sugar
• 1/2 teaspoon ground cinnamon
• 1/2 teaspoon table salt
• 1 pound ripe but firm plums (about 4 standard black ones or 12 smaller Italian plums; I used a mix of both)
• 1 tablespoon (8 grams) all-purpose flour
• 1/4 cup plus 2 tablespoons (6 tablespoons) granulated sugar
• 1 large egg, lightly beaten
• 1 large egg yolk
• 1/3 cup heavy cream
• 1/4 cup milk
• 1/4 teaspoon table salt
• 1/4 teaspoon ground cinnamon
• Grated nutmeg, optional