Trim beans and French (slice thinly on an angle). Bring a pot of water to a boil, salt and blanch beans, uncovered, until just tender, about 4 to 5 minutes.
Drain and rinse to cool (or shock in ice water) (Alternately 2 cups of thawed frozen Frenched beans can be used). Set aside.
Heat 1 tablespoon olive oil in a small sauté pan over medium heat and sauté onion until tender. Remove from heat and toss with beans.
Stir in flour, egg yolks, baking powder, salt and nutmeg and stir to coat. Whip whites until they hold a soft peak, and fold into batter in 2 additions.
Heat a griddle over medium heat with remaining 2 tablespoons of olive oil and drop batter by spoonfuls onto griddle, cooking for about 3 minutes.
Flip over gently and cook 3 minutes more. Repeat with remaining batter until all griddle cakes are made.
Serve with butter or a small dollop of sour cream.