1. In a small bowl, dissolve the yeast in warm milk at 105°F (41°C). Let it sit for 5 minutes.

2. In a large mixing bowl, combine the yeast mixture, remaining water, sugar, salt, and 2 cups (250g) all-purpose flour. Mix until a shaggy dough forms.

3. Gradually add the remaining all-purpose flour and whole wheat flour. Mix until a sticky dough forms.

4. On a floured surface, knead the dough for 10 minutes. Divide into 12 equal pieces. Roll each piece into a ball and place on a parchment-lined baking sheet, leaving 1 inch (2.5 cm) space between them. Cover with a clean cloth and let rest at room temperature for 20 minutes.

5. Cover with plastic wrap and refrigerate for 8 to 15 hours, or overnight.

6. Preheat oven to 425°F (220°C). Remove the dough from the fridge and let it rest for 10 minutes at room temperature. Brush with lightly beaten egg white and sprinkle with sesame seeds and chopped walnuts. Bake in the middle of the oven for 20 minutes, or until golden brown. Handle hot fritters with care to avoid burns.