Melt butter in a small saucepan over medium-low heat, until it begins to sputter and is covered with a layer of foam, 2 to 3 minutes.

Remove from heat and wait until sputtering stops.

Skim off and discard foam; pour clarified butter into a small bowl, leaving behind any milky liquid.

In a large bowl, combine the vegetables and onion.

Sprinkle with flour, salt, chili powder and nutmeg, and toss to coat.

Stir in egg and egg white.

Brush a large skillet with clarified butter and line the bottom with parchment paper.

Brush the paper and sides of the skillet generously with 1 tablespoon more clarified butter.

Heat the skillet over medium heat until hot.

Pour in vegetable mixture and press gently.

Cook, running a spatula around the edges of the skillet occasionally, until bottom is very brown, about 12 minutes.

Place a round platter upside down over the top of the skillet.

Grasp sides of the skillet and platter with oven mitts and invert pancake onto the platter.

Press back in any stuck bits of pancake.

Wipe the skillet clean, place parchment back in the skillet and brush generously with clarified butter.

Slide pancake back into the skillet (browned-side up) and continue to cook over medium heat, loosening edges with a spatula and shaking the pan occasionally to loosen the bottom.

Cook until bottom is browned and crisp and pancake is cooked through, about 12 more minutes.

Invert the skillet again to remove pancake. Cool 5 minutes before cutting into wedges.