Combine warm water, yeast and sugar in the bowl of a stand mixer fitted with a dough hook attachment, or just a large bowl, and allow the yeast to bloom (start to bubble). Allow to sit for 5 minutes.

Add flour, salt and olive oil, and mix on low for 2 minutes until dough starts to come together. Raise speed to medium and mix for another 3 minutes. The dough will be soft — don’t expect it to be super firm, and try to resist the urge of adding more flour.

Place dough in an oiled bowl and cover with plastic or a towel. Allow to rise in a warm spot in the kitchen for 1 hour.

While dough is rising, preheat oven to 450 F. and place a pizza stone in the oven. If you don’t have a pizza stone, you can use a baking sheet (a dark color baking sheet is better for this).

To make the filling: Combine the cheese in a small bowl. Cut butter into 1 tablespoon portions (you will use 2 tablespoons for each cheese bread).

When dough has risen, divide into 2 pieces. Working on top of a lightly floured piece of parchment, gently stretch each piece of dough into ovals 12 inches long.

Spread a quarter of cheese mixture in the middle of each bread, leaving 1/2 inch border all the way around.

Pinch the ends, rolling tight to form points on either side. Add the remaining cheese evenly onto each bread.

Brush the bread with a light coating of olive oil. Allow to rise again 15 minutes.

With the bread remaining on the parchment paper, slide onto the pizza stone or baking sheet. (You can make the breads one at a time or bake simultaneously.)

Bake for 13-14 minutes, or until golden and the cheese is bubbly. Remove cheese bread from oven and gently add egg yolk to the middle of the bread, taking care not to break. Bake for another 1-2 minutes.

Remove from oven and immediately add 2 tablespoons butter to the bread, one on either side of the egg yolk.

Serve by swirling the yolk, cheese and butter all together.