Heat the oven to 400°F (200°C). Line twelve muffin cups and place the pan on a clear counter beside the mixing bowls.
Whisk flour, baking powder, salt, and sugar in a large bowl. Make sure the leavening is evenly dispersed before adding liquid.
In another bowl whisk eggs, oil, milk, sour cream, and vanilla until smooth. Bring any cold mixing ingredients toward room temperature first.
Pour wet ingredients into the dry bowl and fold gently. Stop while a few small flour streaks remain, then fold in blueberries to finish combining.
Divide between the lined cups, filling each about three-quarters full. Scatter optional coarse sugar over the tops without pressing it into the batter.
Bake 18–24 minutes, until tops are golden and spring back. A tester should show no wet batter; avoid piercing a blueberry when checking.
Cool in the pan for 5 minutes, then lift onto a rack so steam can escape from the bases rather than making the liners damp.
Let cool at least 10 minutes before serving warm. Cool fully before storing, keeping the container closed so the muffin crumb does not dry out.
