Gather all your ingredients for the Sourdough Donuts. Preheat your kitchen slightly to encourage the dough to rise beautifully.

In a large mixing bowl, whisk together the all-purpose flour, granulated sugar, salt, baking powder, and baking soda until well combined.

Melt the unsalted butter, then add the sourdough starter, eggs, and vanilla extract. Whisk until smooth and fully blended.

Carefully fold the wet ingredients into the dry mixture using a spatula. Mix gently until just combined.

Cover with a clean kitchen towel and let the dough rise for 1 to 2 hours, or until it doubles in size.

Sprinkle a clean surface with flour and roll the dough out to about 1/2 inch thickness.

Cut out donut shapes with a cutter and allow them to rest for about 10 minutes.

Heat oil to 350°F (175°C) in a fryer or pot.

Fry the donuts for about 1 to 2 minutes on each side until golden brown.

Whisk together powdered sugar, milk, and vanilla extract until smooth for the glaze.