The night before you want to bake your sourdough brioche, mix together a sweet sourdough starter. This is an old baking trick that creates a mild, low-acidity starter: perfect for a briochedough.

Stir together the sweet sourdough starter ingredients, combining thoroughly. Let sit in a warm spot for 8-10 hours, or until it doubles in size.

Once your sweet sourdough starter is ready, start making the dough.

Combine the sweet sourdough starter with the rest of the bread flour, cold milk, salt, sugar, and two eggs in a largemixing bowl. I like to use my stand mixer, but you can also work the dough by hand.

Knead the dough for about 8 minutes. If you’re using a stand mixer, fit it with a dough hook and set it to level 1.5- 2.

Add butter little by little – I like to cut the butter into cubes and add just one cube at a time, making sure each cube is fully incorporated before adding the next one. Scrape down the sides of the bowl frequently.

You’ll know that you’re done kneading when the dough is soft and elastic and passes the windowpane test.

Cover your dough, place in a warm spot, and let it bulk ferment until it is airy and slightly puffy. This usually takes me about two hours at 80F. Be aware that this dough rises faster than the typical sourdough, because it has plenty of starter in it. Review the fermentation chart below for estimate timings.

Divide your dough into eight equal portions, shape into balls, and lay them in your bread pan. They should fit very snugly in a single layer.

Let the brioche proof. You’ll know it’s ready when you poke them and the dough yields, but slowly springs back into shape. This can take one or two hours, or more, depending on the temperature in your kitchen.

Brush the dough with an egg wash made from one beaten egg and a spoonful of milk.

Bake your brioche at 350⁰ for 55-60 minutes. If you have an instant read thermometer, you can check the internal temperature; the brioche is ready when the temperature reaches 195⁰ F.