Brioche dough:

1. Heat up the milk in a small bowl, in the microwave for a few seconds (10-15). The right temperature of the milk should be between 26°C and 32°C to activate the yeast. Stir the crumbled yeast into the warm milk until dissolved.
2. In the bowl of a stand mixer add the flour, sugar, salt, and mix on low speed. Add the eggs, one at a time, the dissolved yeast and keep mixing on low until all the ingredients are well combined. Stop the mixer once to scrape down the sides.
3. Still on low speed, gradually add the butter, a few cubes at a time. Once all the butter has been added, turn the mixer up to medium speed and continue mixing until the dough is smooth and shiny and has pulled away from the sides of the bowl. This should take 15-25 minutes, no less.
4. Gently, shape the dough into a ball and transfer to a lightly oiled bowl. Cover with plastic wrap and let rise at room temperature for 1 hour, or until doubled in size.
5. Punch down the dough, cover again, and refrigerate overnight.
6. Remove the dough from the refrigerator and transfer it to a lightly floured surface. Punch it down a second time and shape it into a rectangle. At this point, the dough is ready to use, but it can also be wrapped in plastic wrap lightly sprayed with oil and stored in the refrigerator for up to two days or in the freezer for up to one week. I cut mine in half, used half and put the other half in the freezer.
7. Butter the muffin tin. Set aside.

Assemble:

1. In a medium saute pan heat olive oil and butter, toss in sliced onions, add sugar, salt, pepper, and paprika, turn heat to low to medium, add water and let saute till onions are nice, soft and caramelized, about 15 minutes cooking time. Set aside to cool a bit.
2. Roll out the dough on a well-floured counter to about a 10-inch width to 12 inches.
3. Spread the pesto on the surface leaving a 1/2 inch border all around. Crumble the goat cheese, add the caramelized onions, the grated Edam (leaving some to sprinkle on top after) and finish with a handful of spinach.
4. Brush the border around with water. Roll the dough up with the filling into a long, tight log. Seal the dampened end onto the log.
5. With a sharp knife, gently cut it in slices. Place the slices in each buttered muffin cup, pulling the sides gently down so as to cover the bottom a bit. Let rest in a warm place for at least 45 minutes to 1 hour.
6. Preheat the oven to 385° F.
7. Brush each brioche with egg yolk, sprinkle with Edam cheese and bake in the preheated oven for about 15 minutes.
8. Let cool on a rack, then gently, with a butter knife, help the brioche to come out of the tin.