In a large bowl, mix sourdough starter, milk, honey, melted butter, and salt.
Add flour gradually until a soft, slightly tacky dough forms.
Cover and let ferment at room temperature for 4–6 hours, or refrigerate overnight.
Preheat oven to 425°F (220°C) and line a baking sheet with parchment paper.
Divide dough into 8 equal pieces. Roll each into a rope and shape into pretzels.
Bring water to a boil and carefully add baking soda.
Dip each pretzel into the water bath for 20–30 seconds, then transfer to baking sheet.
Sprinkle with coarse salt or desired toppings.
Bake for 12–15 minutes until deep golden brown.
Brush warm pretzels with melted butter and serve.