Make batter: In a large bowl, whisk together egg yolks, sugar, salt, and baking powder. Whisk in milk, then flour, whisking just until mostly smooth. (A few tiny lumps proved inconsequential.) Let rest for 10 minutes. Meanwhile, in a second (medium-large) bowl or the bowl of an electric stand mixer, beat egg whites until they hold firm peaks. Fold into egg yolk mixture, trying not to deflate the egg whites. Gently fold in raisins, if using.
Cook pancake: Heat a medium-large skillet (10″ to 12″) over medium heat. Add 2 tablespoons butter or ghee and let warm. Pour batter into pan and spread smooth. Cook for 3 to 4 minutes, lifting an edge to peek occasionally, until it’s a deep golden brown underneath; reduce the heat if it’s browning very quickly. If you feel like you can pull off flipping it in one piece, go for it. I cannot and loosen the edges to slide it onto a large plate. With a potholder on each hand, invert empty frying pan over pancake and plate, grab both together tightly, and quickly flip the pancake back into the pan. Continue cooking until deeply golden underneath on the second side, about 3 minutes.
Shred/tear pancake: There are two ways to do this: You can use two forks or the edge of a sharp spatula to tear/chop the pancake into 1″ to 2″ pieces right in the skillet. However, I prefer to slide it back onto the plate I just used to flip the pancake and chop it there. This allows me to melt another tablespoon of butter in the pan for extra-buttery and lightly crisp edges in the final pancake. Return pancake shreds and any batter that has spilled out — it’s supposed to still be very runny in the center at this point — to the skillet and cook, stirring, until pancake shreds are mostly but not fully cooked through. A custardy center in each bite is ideal.
To serve: Scrape pancake shreds onto plate and sprinkle generously — and I mean generously — with powdered sugar. Serve with lemon wedges, jam, a fruit sauce (applesauce is a popular accompaniment), fresh berries or as shown, with stewed plums/plum compote (zwetschgenröster), directions below. Eat right away.
A quick plum compote (zwetschgenröster): Combine 1 pound fresh black or prune plums* (unpeeled, pitted, and cut into quarters or eighths), 1/3 cup granulated sugar, 1/4 cup water, 1 cinnamon stick or 1 teaspoon ground cinnamon and 1/8 teaspoon (or more to taste) ground cloves over medium heat and bring to a simmer. Simmer gently, stirring occasionally, until fruit is saucy and tender enough that you can break a piece in half with the side of you spoon, about 20 minutes (and up to 25 minute for fruit that’s more broken down). Stir in juice of half a lemon and set aside to cool until needed.