These fluffy, lightly sweet stuffed crepes can be found throughout Vienna at its myriad coffeehouses and konditorei, or pastry shops.
Preheat oven to 350 degrees. Put 4 egg yolks and 1 tablespoon granulated sugar in a heatproof bowl set over a pan of simmering water. Whisk until thickened, about 2 minutes. Remove from heat; whisk in vanilla and zest. Sift together flour and salt; fold into yolk mixture.
Spread 1/4 cup batter in a 3-inch circle on a parchment-lined baking sheet. Repeat, making 8 circles total. Bake until golden, about 8 minutes. Let cool completely on sheet. Transfer to a wire rack.
Whisk together remaining yolk, 1/4 cup granulated sugar, and the wine in a saucepan over medium heat until thickened, 6 to 7 minutes. Remove from heat; whisk 1 minute. Transfer to a bowl. Refrigerate until cold, about 20 minutes.
Beat cream until stiff peaks form. Fold whipped cream and poppy seeds into wine mixture. Refrigerate 1 hour.
Transfer whipped-cream mixture to a pastry bag fitted with a large star tip. Hold each crepe, top side down; fold almost in half. Pipe about 1/4 cup whipped-cream mixture into crepe. Dust with confectioners sugar.
We used Gewurztraminer, but any other lightly sweet white wine, such as Riesling or Tokay (a Hungarian wine), would also be delicious.