Warm the milk until it reaches 105 to 110°F. Pour it into a mixing bowl, and sprinkle the yeast on top. Allow it to bloom for about 5-10 minutes.

Add the granulated sugar and sourdough discard to the yeast mixture. Whisk until combined.

Mix the melted butter and room-temperature egg into the mixture until well incorporated.

Gradually mix in the all-purpose flour and salt until the dough starts to come together.

Knead the dough on a floured surface for about 5-10 minutes until it is smooth and elastic.

Place the kneaded dough in a greased bowl, cover, and let it rise in a warm spot until it doubles in size, about 1-2 hours.

Punch down the risen dough and roll it out into a rectangle about ½ inch thick.

Mix the softened butter, brown sugar, ground cinnamon, and flour for the filling. Spread this mixture over the rolled-out dough.

Roll the dough tightly into a log and cut into 1-inch pieces. Place on a prepared baking sheet.

Cover the rolls with a kitchen towel and let them rise for another 30-45 minutes.

Preheat the oven to 350°F. Bake the rolls for 20-25 minutes until golden brown.

Prepare the glaze by whisking the powdered sugar, milk or cream, vanilla extract, and salt together until smooth.

Drizzle the glaze over the slightly cooled rolls.