Toss the flour, milk, sourdough starter and sea salt together in a blender, and blend until they form a smooth batter. Pour the batter into a mixing bowl, and cover it with cling film or with a tight-fitting lid.

Let the batter sit, covered, at room temperature overnight, or 8 to 12 hours.

Beat the egg yolks together with honey and melted butter. When they're uniformly combined, beat the egg yolk mixture into the pancake batter you made the night before.

In a separate bowl, whip the egg whites with the baking soda until they hold stiff peaks.

Gently fold one third of the whipped egg whites into the pancake batter. Continue folding the remaining egg whites, one third at a time, until you’ve added them all. Incorporate the egg whites into the bowl slowly, carefully and gently, leaving some streaks of unbroken whites, until the batter is light and fluffy. The key to a light sourdough pancake is to avoid deflating the whites.

Set your oven to warm, and place a baking sheet in the oven on the middle rack.

Heat a cast iron skillet or pancake griddle over medium heat, and melt a touch of butter in the pan. When the butter foams, pour a ladleful (approximately ¼ to ⅓ cup) of pancake batter into the pan. Let it cook without disturbance until you see bubbles forming in the center of the pancake. Flip the pancake and continue cooking it 1 to 2 minutes further until cooked through. Transfer the pancake to the baking sheet in the oven to keep it warm.

Continue cooking pancakes, one at a time, and adding more butter to the pan as needed until you’ve exhausted the batter.

Serve with additional butter, maple syrup or homemade blueberry syrup.