Whole Grain Chocolate Babka

Ingredients

• 1 1/2 (0.25oz) package (7g) or 2 1/4 teaspoons Platinum Yeast
• 1/3 cup (66g) granulated sugar
• 1/4 cup (40g) potato flour
• 2 tablespoons vital wheat gluten
• 3/4 teaspoon table salt
• 2 cups (250g) white whole wheat flour, divided
• 1 3/4 cups (218g) all-purpose flour, divided
• 3/4 cup (168g) unsalted butter
• 1 cup plus 2 tablespoons (265ml) milk
• 2 large eggs
• 2 egg yolks (reserve 1 egg white egg wash)
• 2 teaspoons vanilla
• 1/4 cup (50g) granulated sugar
• 20 ounces (540g) semi-sweet chocolate, chopped finely
• 2 tablespoons ground cinnamon
• 5 tablespoons unsalted butter
• 1/4 cup plus 2 tablespoons (46g) white whole wheat flour
• 1/4 cup plus 2 tablespoons (75g) granulated sugar
• 1/4 cup (56g) unsalted butter
• Egg wash: 1 egg white mixed with 1 tablespoon water