- 4 ounces (1 stick) unsalted butter, cut into 1/2-inch pieces, at room temperature
- 1/2 cup water
- 1/4 cup sugar
- 1/4 teaspoon salt
- 1 cup all-purpose flour
- 3 eggs
- 1 egg yolk
- 2 teaspoons lemon zest (from 1 lemon)
- Vegetable oil, for frying
- 1/4 cup whipping cream
- 1 tablespoon coffee liqueur (recommended: Kahlua)
- 2 teaspoons espresso powder
- 2 cups powdered sugar
- Water, as needed
- 1 (3-ounce) chocolate bar, optional
- 1 cup raspberries, optional
For the doughnuts: In a medium saucepan, combine the butter, water, sugar, and salt over medium heat. Bring to a rolling boil, stirring occasionally. Boil for 10 seconds. Remove the pan from the heat and add the flour. Using a wooded spoon, quickly stir the mixture until all the flour is fully incorporated and forms a thick dough. Return the pan to the heat and stir continuously for 2 minutes. Scrape the mixture into a stand mixture fitted with a paddle attachment. With the machine running on medium speed, add the eggs and egg yolk, 1 at a time until fully incorporated. Beat the mixture for 4 to 5 minutes until thick and glossy. Add the lemon zest and beat until smooth. Refrigerate the dough for 15 minutes.
For the glaze: In a medium bowl, whisk together the cream, coffee liqueur, and espresso powder until smooth. With a wooden spoon, gradually stir in the powdered sugar until smooth. If the glaze is too thick, stir in the water, 1/4 teaspoon at a time.
In a large heavy-bottomed saucepan, pour in enough oil to fill the pan about a third of the way. Heat over medium heat until a deep-frying thermometer inserted in the oil reaches 375 degrees F. (If you don't have a thermometer a cube of bread will brown in a couple of minutes.)
Using a small ice cream scoop or 2 small spoons, carefully drop scoops (about 1 tablespoon) of the dough into the oil. (Do not crowd the pan,) Cook for 3 to 3 1/2 minutes, turning occasionally, until the zeppole are golden and puffed. Drain on paper towels. Repeat until all of the dough has been used. When the zeppole is cool enough to handle, dip the top halves in the glaze.