In a large bowl, whisk together sourdough starter, warm milk, honey, melted butter, egg, and salt.
Gradually add flour until a soft, slightly tacky dough forms.
Cover and allow to ferment at room temperature for 6–8 hours, or refrigerate overnight.
Turn dough onto a lightly floured surface and roll to about ½-inch thickness.
Cut dough into 10-12 pieces and form into donut shapes. Let rest 30–45 minutes until slightly puffy.