In a large mixing bowl (or stand mixer bowl), combine the warm milk, active dry yeast, and 2 tablespoons of granulated sugar. Stir gently and let sit for 5-10 minutes until foamy.

Add the sourdough discard, egg, and 1/4 cup melted butter to the yeast mixture. Whisk until well combined.

In a separate bowl, whisk together the all-purpose flour and salt.

Gradually add the dry ingredients to the wet ingredients, mixing with a wooden spoon or the dough hook of a stand mixer until a shaggy dough forms. Knead for 5-7 minutes until the dough is smooth and elastic. If kneading by hand, turn the dough out onto a lightly floured surface.

Lightly grease the mixing bowl, place the dough back in, cover with plastic wrap or a damp towel, and let rise in a warm place for 20-30 minutes, or until slightly puffy. It won't double in size like a traditional yeast dough, but it should show some activity.

While the dough is rising, lightly grease a 9x13 inch baking dish.

In a small bowl, combine the 1/2 cup softened butter, brown sugar, and ground cinnamon. Mix until a smooth, spreadable paste forms.

Once the dough has rested, gently punch it down and turn it out onto a lightly floured surface. Using a rolling pin, roll the dough into a large rectangle, approximately 12x18 inches.

Spread the cinnamon filling evenly over the entire surface of the dough, leaving a small border (about 1/2 inch) along one of the longer edges.

Starting from the longer edge opposite the border, carefully roll the dough into a tight log. Pinch the seam closed to seal. Using a sharp knife or unflavored dental floss, cut the log into 12 equal slices (about 1.5 inches thick).

Place the sliced rolls cut-side up into the prepared baking dish, leaving a little space between each roll.

Cover the baking dish loosely with plastic wrap or a damp towel and let rise in a warm place for another 15-20 minutes while you preheat the oven.

Preheat your oven to 375°F (190°C).

Bake the cinnamon rolls for 20-25 minutes, or until golden brown and the centers are cooked through. If they start to brown too quickly, you can loosely tent them with foil.

While the rolls are baking, make the frosting. In a medium bowl, beat together the softened cream cheese and softened butter until smooth and creamy. Gradually add the powdered sugar, beating until fully incorporated. Stir in the vanilla extract and 1-2 tablespoons of milk or cream until the frosting reaches your desired consistency. It should be thick but spreadable.

Once the cinnamon rolls are out of the oven, let them cool in the pan for 5-10 minutes. Then, spread the cream cheese frosting generously over the warm rolls. Serve immediately and enjoy your Quick Sourdough Discard Cinnamon Rolls!