Whisk the water and yeast in a small bowl. Let stand for 10 minutes until completely dissolved. Set aside

In the bowl of a stand mixer fitted with a dough hook, sift together the pastry flour, all-purpose flour, sugar and salt.

Turn the mixer on low and add 6 eggs to the bowl 1 at a time beating well after each addition.

Slowly add the yeast and continue beating at low speed for 5 minutes.

Stop the mixer and scrape down the sides of the bowl. Turn the mixer on low and beat for an additional 5 minutes.

Add the butter cubes 1/3 at a time, beating for about 1 minute after each addition. Once the butter has been added, beat for 10 more minutes until the dough is smooth.

Transfer the dough to a lightly oiled bowl and cover with plastic wrap. Let the dough rest in a warm place until doubled in size, approximately 3 hours.

Turn the dough out on a well floured surface and gently knead out the air bubbles. Return the dough to the bowl, cover with plastic wrap and refrigerate overnight.

Turn the dough out onto a floured surface and divide the dough in half. Then divide each half into 5 equal pieces.

Shape each piece into a ball and place on a baking sheet lined with parchment approximately 4 inches apart.

Allow the dough to rise, uncovered, in a warm place until it rises about double in size, approximately 2 hours.

Preheat the oven to 350 degrees.

Beat 1 egg with 1 tablespoon of water and brush the tops of each dough ball with the egg wash. Sprinkle with sesame seeds, if desired.

Bake the brioche until it is golden brown on top, approximately 25 minutes. Remove from the oven and allow to cool for 2-3 minutes.

Transfer the rolls to a cooling rack and cool completely.

If not serving immediately, wrap the hot bread in foil and set aside at room temperature for up to 2 days.