In the bowl of a stand mixer, combine the instant yeast, water, sugar, sourdough discard, all-purpose flour, salt, cubed butter, and egg. There is no need to warm the liquid before combining unless blooming dry active yeast.

Attach the dough hook and mix on low speed until the ingredients come together into a rough, homogenous dough.

Increase the speed to medium and knead for about 4 minutes to develop the gluten. To check if the dough is ready, use a windowpane test by pinching off a small piece and gently stretching it. If it forms a thin, translucent sheet without tearing, the gluten has developed properly or simply look for a smooth, soft dough that pulls away cleanly from the sides of the bowl.

Lightly oil or spray a medium bowl with non-stick spray and transfer the dough into it. Lightly oil the top of the dough, cover and allow to bulk proof for about 45 minutes, or until it has doubled in size. This rising time will vary based on the temperature of your kitchen.

Divide the dough into 12 equal pieces, about 78 g each, using a knife or a bench scraper.

Grease a 9 x 13-inch baking dish or pan with non-stick spray or softened butter before you begin shaping the rolls.

Working with one piece of dough at a time, shape each roll by folding the edges into the center, then place the seam-side down on the counter and roll quickly between your thumb and other fingers. The goal is to create a push and pull motion that gently tightens the roll into a ball. To do this, don’t let the dough roll around in your hand. Push the dough away from you using your thumb, then sweep it back toward you with your other fingers, and repeat. Make sure to work quickly to prevent the dough from sticking excessively to your hands or the counter. Allowing it to stick just a little to the counter will actually help you form a nice, tight roll.

Place it in the baking dish and repeat with the remaining rolls. Cover with plastic wrap and proof in a warm spot for an hour until they are tripled in size and feel light and airy when gently touched with your finger.

Meanwhile, preheat the oven to 350ºF using the conventional setting without a fan.

Before baking, you can brush the tops with a well-beaten egg. Egg wash will give the rolls a shiny, golden finish. Be careful not to let it run down the sides of the dish or pool.

Bake rolls in a preheated oven for 20-25 minutes until they are golden brown. You can also test with an instant-read thermometer. This is an enriched dough so it should read 185ºF.

Remove from the oven and brush the top of the rolls with melted butter.

Serve slightly warm or at room temperature.