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Sourdough potato fastnachts on parchment paper with powdered sugar dusting and torn pieces showing soft crumb with cinnamon stick and whole nutmeg
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Sourdough Potato Fastnachts

A naturally leavened Pennsylvania Dutch fastnacht made with sourdough starter and potato. Mix the dough in the evening, let it rise overnight, and fry the next morning. No commercial yeast needed, although that option is offered in the note section and blog post.
Course: Breakfast, Snack
Cuisine: American, Pennsylvania Dutch
Keyword: fasnachts, Fastnacht Day, fastnachts, Fat Tuesday, fried dough, molasses, overnight sourdough, Pennsylvania Dutch donuts, potato donuts, Shrove Tuesday, sourdough donuts
Servings: 12 Fastnachts
Calories: 320kcal
Author: Noelle Reed

Equipment

  • Small Pot for boiling potatoes
  • fork for mashing potatoes
  • - Stand mixer with dough hook or hands for kneading
  • Large bowl with lid or plastic wrap
  • Rolling Pin
  • knife to cut your dough
  • sheet pan for proofing with lid or another sheet pan turned upside down on top to create a cover
  • Parchment paper
  • deep pot, dutch oven or electric fryer
  • thermometer
  • wire rack
  • Paper towels

Ingredients

Dough

  • 75 g active sourdough starter generous 1/2 cup, fed 4 to 8 hours earlier, bubbly and at peak
  • 115 g mashed potatoes 1/2 cup, plain, mashed very smooth, no butter or milk added
  • 120 g potato water 1/2 cup, cooled to below 90 degrees F
  • 90 g granulated sugar scant 1/2 cup
  • 57 g butter 1/4 cup, softened to room temperature, or lard
  • 1 large egg room temperature
  • 60 g whole milk 1/4 cup
  • 6 g fine sea salt 1 teaspoon
  • 1/8 teaspoon freshly grated nutmeg
  • 525 g all purpose flour about 4 cups + 3 tablespoons

For Frying

  • Avocado oil lard, vegetable shortening, or neutral oil, 3 to 4 inches deep in pot
  • Oil heated to 360 degrees F

For Topping (choose your style)

  • Powdered sugar
  • Granulated sugar
  • Cinnamon sugar
  • Dark molasses or blackstrap molasses spread inside a split fastnacht

Instructions

Evening

  • Boil 1 medium russet potato (peeled, cubed) in about 2 cups of water until very soft. Reserve the potato water. Mash the potato very smooth with no lumps. You need 115g (1/2 cup) mashed potato and 120g (1/2 cup) potato water. Let both cool to warm (below 90 degrees F) or room temperature before using.
  • In a stand mixer fitted with the dough hook, combine the sourdough starter, mashed potatoes, potato water, sugar, egg, milk, salt, and nutmeg. Mix on low speed until combined.
  • Add the 525g flour, then place the butter on top, broken into acorn size pieces. Mix on low until it comes together, then increase to medium low and mix for 5 minutes. The dough should be smooth, soft, and just slightly tacky, and it should pull cleanly from the sides of the bowl. If mixing by hand, knead for 8 to 10 minutes until the dough is smooth and springs back when poked. If you are measuring by weight, you should not need additional flour. If you are using cup measurements, there can be slight variation in volume, so if the dough is sticky and not clearing the sides of the bowl after 5 minutes, add a tablespoon of flour at a time, being sure it works in, until it does. But do not over flour it will make your fastnachts too dense.
  • Transfer the dough to a greased bowl. Cover with a lid or plastic wrap. I like to use a plate
  • Leave on the counter overnight, 8 to 12 hours. The dough should at least double, ideally close to triple in size. If your kitchen runs cold (below 68 degrees F), the dough will take longer to rise, so start your dough earlier in the day.
    Side by side comparison of sourdough fastnacht dough in a stand mixer bowl showing small dough ball after kneading on top and large risen dough filling the bowl the next morning on bottom

Morning

  • Turn the risen dough out onto a well floured surface.
  • Roll to about 3/4 inch thick. You don’t have to be precise, but if you want a guide, roll into a 9 by 12 inch rectangle and score lines every 3 inches to create a grid of 12 squares.
    Sourdough potato fastnacht dough rolled out to three quarter inch thick on a floured surface with a ruler for measurement and butter, starter, molasses, and eggs in the background
  • Cut into rectangles with a knife.
    Knife cutting sourdough potato fastnacht dough into twelve squares on a floured wooden surface with ruler visible at the bottom edge
  • Place on a parchment lined sheet pan, spaced about 1.5 inches apart. Cover with a lid or an upside down sheet pan of the same size. You can also make/buy parchment paper squares and place the fastnachts on that. (see the frying instructions for why)
    Twelve square cut sourdough potato fastnachts arranged in rows on a parchment lined sheet pan before proofing
  • Let proof for about 2 hours at room temperature, or until the pieces are noticeably puffy and pillowy. When you poke one with a floured finger, the indent should spring back slowly. In a cold kitchen this may take longer.
  • Heat frying fat to 360 degrees F. Use a deep pot/Dutch oven or electric fryer with at least 3 to 4 inches of oil. Use a thermometer.
  • Place fastnachts top side down into the oil. Fry 2 to 3 at a time, about 2 minutes per side, until deep golden brown. Do not crowd the pot. Give the oil time to recover between batches.
  • Alternatively you can cut your parchment around the fastnacht and drop in parchment side up. fry for the 2 minutes and then flip and then gently remove the parchment paper from the oil.
  • Drain on paper towels or a wire rack set over a sheet pan.
  • Top while still warm with your choice of powdered sugar, granulated sugar, cinnamon sugar, or split open and spread with molasses.

Notes

  • The potato water is full of starch that feeds the sourdough and creates the classic fastnacht texture. Do not skip it.
 
  • Use your starter at peak activity. A sluggish starter will give flat fastnachts.
 
  • If the dough hasn’t doubled overnight, your kitchen may be too cold or your starter wasn’t active enough. Give it more time in a warmer spot.
 
  • A shorter fry time can leave the center slightly underdone, which shows up as a gummy texture when reheated. Make sure you are frying the full 2 minutes per side at 360 degrees F.
 
  • If the dough only doubled overnight rather than tripled, give the cut pieces extra proofing time. Underproofed fastnachts will sink in the oil and puff unevenly.
 
  • For leftovers, cut in half and place cut side down in a preheated pan to toast. They also reheat at 350 degrees F in the oven for about 5 minutes.
 
  • Wrap individually in foil inside a freezer bag and freeze for up to 3 months.
 

For a yeasted version

Replace the sourdough starter with 7g active dry yeast (one packet or 2.25 teaspoons) dissolved in the warm potato water.
 
Increase the flour to 560g (about 4.5 cups) and increase the milk to 100g (scant 1/2 cup).
 
The method is the same. Mix in the evening, rise overnight, roll, cut, and fry in the morning.
 
The yeast amount is low on purpose. A small amount of yeast with a long overnight rise develops better flavor than a fast rise with lots of yeast. more thorough instruction on the blog.
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