Make the dough: Combine the starter, pumpkin puree, milk and sugar in a large bowl. Stir until the starter is fully dissolved.
113 grams sourdough starter, 150 grams pumpkin puree, 75 grams milk, 50 grams cane sugar
Fold the all-purpose flour and salt into the pumpkin mixture. Stir until a shaggy dough forms.
400 grams all-purpose flour, 9 grams salt
Knead the butter into the dough 1 tablespoon at a time, wait until the dough absorbs the butter before adding more. The dough will gradually feel less oily as you massage the butter into the dough.
56 grams unsalted butter
Cover the bowl with plastic wrap and let the dough rest for 1 hour.
Knead the dough: Knead the dough until it looks smooth, about 5 to 10 minutes. The dough should feel stretchy and look smooth. Gather the dough into a tight ball and place it in a clean, lightly-oiled bowl. Cover the bowl with plastic wrap and let the dough rise in a warm place.
Bulk fermenation: Let the dough rise until it has doubled in volume and feels bubbly. This can take about 4 to 6 hours, but it's extremely important that you allow your dough to rise or your rolls will turn out tough.
Cold proof: Deflate the dough and place it in the refrigerator to proof overnight. (see note)