01 - In a small bowl, combine lukewarm milk and water. Sprinkle over the yeast and 1 teaspoon sugar. Let stand for 5 to 10 minutes until frothy.
02 - In a large bowl, whisk together all-purpose flour, remaining sugar, salt, and lemon zest.
03 - Add eggs, melted butter, vanilla extract, and activated yeast mixture to the dry ingredients. Mix to form a sticky dough.
04 - Knead dough on a floured surface for 8 to 10 minutes until smooth and elastic. Place in a greased bowl, cover, and allow to rise for 1 hour or until doubled in size.
05 - Punch down dough and roll out to 1/2-inch thickness. Cut rounds with a 3-inch round cutter.
06 - Arrange dough rounds on a floured tray, cover, and let rise for 30 minutes.
07 - Heat neutral oil in a deep pot to 350°F. Fry pączki in batches for 1 to 2 minutes per side until golden brown. Drain on paper towels.
08 - When cool enough to handle, use a piping bag to fill each donut with assorted fillings, mixing and matching as desired.
09 - Prepare a simple icing by mixing powdered sugar with water and food coloring if preferred. Dip tops of donuts into icing and decorate liberally with toppings.
10 - Allow donuts to set for 10 minutes before serving.