In a large bowl, whisk together the sourdough starter and milk until the starter is fully dissolved and the mixture is uniform in color.

Add in the egg, sugar, melted butter, and vanilla until everything is well incorporated and the sugar has begun to dissolve.

Next, sift in your flour and salt and mix until no lumps remain and the dough forms a shaggy, cohesive mass.

After mixing, cover the dough with a damp cloth and allow it to rest for 30 minutes (autolyse) to ensure full hydration of the flour particles.

After the rest period, uncover the dough and knead in a stand mixer with a dough hook on medium speed for exactly 12 minutes, or until the dough pulls away from the sides of the bowl and feels like smooth silk.

Cover the bowl with a damp cloth and allow the dough to rise overnight for 8-10 hours at 70°F(21°C). The dough is ready when it is light, airy, and has doubled in size.

Turn the dough out onto a well floured surface. Use a rolling pin to roll the dough into 1/2 inch thickness. If the dough resists being rolled, allow it to relax for 10 minutes and try again.

Use a 2 3/4" biscuit cutter to cut out the donuts. Gather scraps and allow them to rest for 30 minutes before re-rolling to avoid tough final donuts.

Take a cut donut and pierce the center with a chopstick or skewer. Spin the dough around the chopstick until the center hole has stretched to a 1" width to ensure it doesn't close up during the rise.

Place the donuts on a parchment lined surface 2" apart and cover them with a damp cloth. Allow the donuts to rise at room temperature for about 2 hours, or until they have risen by 50% of their original size (they should feel light like a marshmallow).

Mix the standard glaze together (or maple smoked salt glaze) at the end of the second rise: In a small bowl stir together the milk and powdered sugar until you have a thin runny mixture with no lumps.

Preheat the oven to 350°F(180°C). Transfer the parchment paper and risen donuts onto a large baking sheet.

Bake on the center rack for 13-15 minutes until they have just set but have not taken on much color.

While donuts are baking, heat 1" of coconut oil in a deep sided frying pan over medium heat until it reaches 350°F(180°C). Monitor temperature constantly.

Add a few pre-baked donuts to the hot oil at a time. Heat for one minute, or just until the bottoms begin to turn golden in color.

Flip the donuts and heat the other side for one minute or until they begin to turn golden.

Transfer the cooked donuts to a cooling rack lined with paper towels to soak up any surface oil.

Allow donuts to cool for a few minutes, then dip one side into the prepared glaze. Place the freshly glazed donuts glaze side up on a drying rack, and allow the glaze to set for 10 minutes before serving.