Put one tablespoon of sourdough starter into a clean container or pint size jar. Feed it with 60g water and 60g white flour. Stir until no dry flour is left. Let it sit at room temp 6-12 hours until active (doubled in volume, full of large bubbles, and smells fragrant like ripe fruit)

Scald the milk: Add more whole milk than the recipe calls for to allow for evaporation. Heat the milk over medium to medium-high heat until it is steaming and proteins begin to stick to the pot. Temperature will be 130 to 140 degrees F. Don't let it foam. Transfer 100g of your scalded milk to the bowl of a stand mixer, large bowl, or a separate glass carafe to cool down to 90-100 degrees F.

Knead your dough into a smooth, soft ball. It will take 5 to 8 minutes to get combined and soft until it pulls away cleanly from the sides of the bowl. Kneading by hand will take 8 to 12 minutes.

Now, it is time to knead in the softened unsalted butter. Add it one tablespoon at a time with kneading in between each addition. Continue kneading until the butter is completely incorporated into your dough and it pulls away cleanly from the sides of the bowl or kneading surface and is a soft smooth ball.

Place your dough into an airtight container or use a large clean bowl covered with plastic wrap. Keep your dough at room temperature for 4 to 8 hours for the bulk fermentation or first rise until it doubles.

In a small saucepan, melt the butter and put it in a small bowl to cool.

In a small bowl, mix the sugar and cinnamon until they are combined.

Prepare a baking sheet by lining it with parchment paper.

Place the dough on a lightly floured surface and use a lightly floured rolling pin to roll the dough into a circle that is 11-12 inches wide.

Use a rolling pizza cutter or a knife to cut the circle into thirds and then cut each third portion into thirds again to create 9 wedges of dough that are about equal in size.

Put as many of the triangles of dough* onto your lined baking sheet as you can fit and bring them over to a dining table along with a bowl of large marshmallows, the bowl of melted butter, and the bowl of cinnamon sugar.

Before you begin shaping, make sure to preheat your oven to 375 degrees F since they will go directly into the oven after shaping without the typical proofing time.

Take a marshmallow and roll it in the butter until it is completely covered. Place the butter coated marshmallow on the larger end of the triangle of dough. Take a spoon (about a teaspoon to half tablespoon size) and scoop up the cinnamon sugar and sprinkle over the marshmallow until it is covered.

Take the two ends of the base of the triangle and fold them to meet one another and pinch them together to create a seam. From that wider end, roll the dough coated marshmallow up the tip of the triangle and then pinch any opening to completely seal the marshmallow into the dough. Place the marshmallow filled roll onto the parchment lined baking sheet.

Repeat with the rest of the dough and marshmallows until all the rolls have been made.

Place your rolls into the hot oven to bake for 14 to 17 minutes. Once they look slightly golden and baked, turn your oven to 375 degrees F on the convection setting. Bake for 1 to 2 minutes with the convection setting.

Cool these rolls on a cooling rack for at least 5 minutes. Then serve!