Line a half sheet pan with parchment paper (the photo shows the 10-inch Mauviel pan – if you use something similar, generously grease the sides and bottom of the pan with butter).
On a lightly floured surface, fold the dough over 3-4 times and then form it into a ball. Let the dough rest for 15-20 minutes.
Roll the dough into a 1/4-inch thick rectangle. Brush the entire surface with 2 tablespoons melted butter. Start with 1/2 cup of jam, and spread the jam over the dough. If more jam is needed, add more until there is a thin layer over the dough (you don’t want too much jam, or the next steps will be extra messy).
Roll the dough up, starting at the short end. Using a sharp kitchen knife or scissors, cut the log into 12 equal pieces.
Set the buns in the prepared pan, 1 1/2 to 2-inches apart. Loosely cover the buns and let them rest between 1 1/2 to 2 hours, until they have almost doubled in size. (You can set these up the night before and let them rest overnight in the refrigerator. In the morning take them out and let them sit on the counter for about 45 minutes to an hour.)
Adjust an oven rack to the middle position, and heat the oven to 350F. Generously cover the tops of the buns with the streusel before putting into the oven, gently pressing the streusel into the buns (there will be some streusel left over).
Bake for about 22 to 27 minutes, just until the centers are set when poked with your finger, and the tops are light golden brown. Transfer the pan to a wire rack and let cool 10-15 minutes before icing.