Buttermilk Sourdough Glazed Donuts

Directions:

1. Warm the buttermilk in a small saucepan over medium-low heat until warm (but not hot) to the touch, about 110-degrees Fahrenheit (45-degrees Celsius).
2. Pour the warm buttermilk into a large mixing bowl. Add the sugar and stir, then sprinkle the yeast over the top. Let rest for 5 to 10 minutes, until the yeast foams. 
3. Meanwhile, melt the butter and let cool slightly before using. 
4. Once the yeast has foamed, add the flour, sourdough starter, eggs, melted butter, and salt. Mix until a shaggy dough is formed, then begin kneading until the dough is soft and smooth. 
5. Loosely cover the bowl with a linen towel or plastic wrap. Transfer the dough to the fridge for about 45 minutes, or until cold. While the dough chills, line a sheet pan with parchment and set aside. 
6. Turn the chilled dough onto a lightly floured surface and roll to about ½ inch thickness. Using a round cutter, lid, or jar, cut the dough into circles. Use a smaller circle to cut out the donut holes.
7. Place the donuts and donut holes on the prepared sheet pan and cover with a towel to rise at room temperature for 45 to 50 minutes, or until puffed and almost doubled in size. 
8. As the donuts rise, make the glaze by whisking together 2 cups (226 grams) powdered sugar with the heavy cream, vanilla extract, and lemon juice until smooth and glossy. If the glaze is too thin, add up to 1 cup (113 grams) powdered sugar to thicken it. If the glaze is too thick, add a splash of cream to make it thinner. 
9. Once the donuts have risen, heat the oil in a large, heavy-bottomed pot until it reaches 350-degrees Fahrenheit (180-degrees Celsius). This temperature is hot enough that you can cook the donuts for a short time, flipping only once. If the oil is too cold, your donuts will soak up too much oil.
10. Working in small batches, add the donuts to the hot oil. Fry for 1 minute on each side, then remove the donuts with a slotted spoon and transfer to a towel or cooling rack. 
11. Once the donuts are cooled just enough to handle, dip them into the glaze. Set on parchment paper to cool before enjoying and drizzle any extra glaze over the donuts, if desired.