In a small bowl, dissolve the yeast in the warm water and set aside for 5-10 minutes until it becomes foamy.
In a small saucepan, scald the milk over medium heat (heat until just before boiling).
Remove from heat and stir in the butter and sugar until melted.
Pour this mixture into a large mixing bowl and let it cool to a lukewarm temperature.
Once the milk mixture is lukewarm, stir in the activated yeast.
Add the salt and about 2 cups (480 ml) of the whole wheat flour, beating with an electric mixer until smooth.
In a separate small bowl, lightly beat the whole egg and the 4 egg yolks together.
Reserve about 2 tablespoons (30 ml / 1 fl oz) of this mixture for the egg wash later.
Add the rest of the beaten eggs to the dough and beat again until smooth and fully incorporated.
Gradually add the remaining flour, about a cup at a time, stirring with a wooden spoon until the dough becomes too stiff to mix.
Turn the dough out onto a well-floured surface.
Knead for 10-15 minutes, adding small amounts of flour as needed to prevent sticking, until the dough is smooth and elastic.
Form the dough into a ball and place it in a large, well-buttered bowl.
Turn the dough over once to coat all sides with butter.
Cover the bowl with a clean towel and let it rise in a warm, draft-free place for about 1. 5 hours, or until doubled in size.
Punch the dough down to release the air and divide it into two equal pieces. On a lightly floured surface, pat each piece into a 14x6 inch oblong.
Slice each oblong into 3 even strips, leaving them connected at one end. Braid the three strips together, tucking the final ends underneath and pinching to seal.
Carefully place each braided loaf into a buttered medium-sized loaf pan.
Cover with a towel and let them rise for another 30 minutes, or until they have risen about half their size again.
Preheat your oven to 375°F / 190°C.
Stir the 1 teaspoon (5 ml / 0.2 fl oz) of cream into the reserved egg mixture to create an egg wash. Gently brush this wash over the tops of both loaves and sprinkle generously with sesame seeds.
Bake for 45 to 50 minutes, or until the loaves are a deep golden brown and sound hollow when tapped on the bottom.
Let cool in the pans for a few minutes before transferring to a wire rack to cool completely.
Don't skip the egg wash! It's the secret to achieving that beautiful, shiny, golden-brown crust and helps the sesame seeds stick.
