Add the yeast and the ½ teaspoon sugar to the bowl of a stand mixer. In a measuring cup, microwave ¼ cup water until it is 115 degrees F. Add the water to the yeast mixture. Let sit until foamy, about ten minutes.

Once the yeast has activated, add the sugars, whole milk, vanilla extract, egg, and egg yolk to the bowl. Whisk to combine.

Fit the mixer with the hook attachment. Add the flour and salt to the mixture in the bowl. Turn the mixer on medium high and knead for five minutes. Add the softened butter and knead on medium/high for another five minutes until well incorporated.

Add the sticky dough to a well-greased bowl. Cover with a kitchen towel and let rise in a warm area for an hour and a half to two hours, until it doubles in size.

When the dough has risen, lightly flour a work surface. Turn the dough out onto the surface and knead for 2 minutes. Lightly flour the top of the dough along with a rolling pin. Roll the dough out into a 10×20 inch rectangle.

Lightly brush the dough with the melted butter. Spread the sugars, walnuts, and jam out in an even layer on the dough, leaving a one inch border.

Start from the top, and gently yet tightly roll the dough into a cylinder. Pinch along all the edges to seal. Place the dough seam-side down on a cutting board. Slice the roll into eight equal pieces.

Arrange the pieces, cut side up, in a 9×13 inch greased baking pan or springform pan. Cover with plastic wrap and let rise in a warm place for two hours or let rise in the refrigerator overnight and then just let come back to room temperature in the morning before baking.

Preheat the oven to 375 degrees F. Bake the rolls for thirty minutes.

While the rolls bake, whisk together the powdered sugar and buttermilk in a small mixing bowl. When the rolls are done, remove from oven, and cover with glaze. Serve immediately.