Whole-Wheat Chocolate Babka

Ingredients

• ½ cup warm water
• ½ ounce (2 envelopes; 14g) dry yeast
• ½ cup (100g) plus 1 teaspoon sugar, divided
• 3 cups (375g) all-purpose flour
• 2 cups (250g) white whole-wheat flour
• ½ cup (120ml) canola oil
• ½ cup (1 stick; 113g) margarine, at room temperature at least 30 minutes
• 3 large eggs plus 1 egg white (reserve yolk for glazing)
• 1½ cups (300g) sugar
• ½ cup (40g) unsweetened cocoa
• 1 cup (2 sticks; 226g) margarine, at room temperature for at least 30 minutes
• 1 cup (180g) mini-chocolate chips
• 2 teaspoons water plus reserved egg yolk