1-Mix Dough: Combine room temperature dry ingredients (flour, sugar, baking powder, baking soda, salt). In a separate bowl, whisk wet ingredients (buttermilk, eggs, yogurt/sour cream, melted butter, vanilla). Gently fold wet ingredients into dry ingredients until just combined. Carefully fold in blueberries. Avoid overmixing.

2-Chill: Cover dough and refrigerate for at least 30 minutes.

3-Fry: Heat neutral oil (avocado, vegetable, canola, or peanut) to 350-370°F (175-188°C) in a heavy pot. Use a 1-tablespoon cookie scoop to drop portions of chilled dough into the hot oil. Fry in batches until golden brown, turning occasionally (about 2-3 minutes per batch).

4-Drain & Cool: Remove donut holes with a slotted spoon and drain on paper towels or a wire rack. Let cool for 5-10 minutes.

5-Fill: Fit a piping bag with a round tip. Fill the bag with lemon curd. Gently insert the tip into the side of each slightly cooled donut hole and pipe in the filling until plump.

6-Glaze: While the filled donut holes are still slightly warm, dip the tops into the prepared vanilla bean buttermilk glaze. Allow excess glaze to drip off before placing on a rack to set.