In a large bowl, combine flour, sugar, and yeast. Mix well.

Add the melted butter, warmed (not hot) milk, egg yolks, and salt. Stir and knead the dough for about 5 to 8 minutes, until it forms a ball and pulls away from the sides of the bowl.

Place the dough in an oiled bowl, and turn it so that the top and bottom are now thinly coated with oil. Cover with plastic wrap, and place in a warm place to rise for 1 to 1 ½ hours, or until doubled in size.

Combine the sugar and cinnamon in a small bowl, and set aside.

Turn the risen dough out onto a lightly floured surface.

Roll out the dough into a rectangle, about 16x19 inches. The dough should be an even thickness all the way across.

Spread the softened butter over the dough, and then sprinkle the cinnamon sugar evenly over the butter.

Roll the dough up tightly to make a long log. Turn the log over so that the seam is underneath.

Cut the dough into 12 even portions, using a very sharp knife.

Place in a greased baking pan, evenly spaced.

Cover the rolls with plastic wrap, and allow them to rise for about 30 minutes until they are doubled in size.

During this rise, preheat the oven to 350°F.

Once the cinnamon rolls have risen, remove the plastic wrap and bake them for 17 to 20 minutes, or until golden-brown.

Remove them from the oven and set aside until the glaze is prepared.

Combine the powdered sugar and heavy cream in a mixing bowl, and whisk until smooth.

Spread the glaze over the warm cinnamon rolls.

If you wish, add an extra layer or sprinkle of glaze just before serving.