In a stand mixer bowl, add both flour types, dry yeast, sugar and salt (place the salt not directly near or on the dry yeast - it will only cause it to not work as it stays with the salt).
Attach the kneading hook and mix.
Add the water gradually while mixing.
Add the eggs one at a time and continue mixing.
Add the olive oil and mix until all dough is unified.
Flour the bowl and make the dough into a ball shape.
Let the dough rise for an hour and a half or until it doubles in size.
After the dough has risen, set the oven to 180°C / 350°F fan.
Divide the dough to two and each part to 3.
Make strings from the 3 parts.
Braid each 3 parts to a challah shape.
Place the 2 braided loaves on a baking pan lined with baking paper.
Brush with egg wash and sprinkle sesame and nigella seeds.
Bake for 40 minutes.
Cool at room temperature.
Have a slice and Shabbat Shalom!