In a mixing bowl, combine all-purpose flour, sugar, and a large egg until a dough forms. Knead the mixture on a lightly floured surface for about 5 minutes until it becomes smooth and elastic. Once finished, wrap the dough in plastic wrap and let it rest at room temperature for 30 minutes to allow the gluten to relax.

Divide the rested dough into manageable portions, taking one at a time. Roll it out to about 1/8 inch thickness on a floured surface. Use a 3-inch round cutter to cut out circles. Keep any unused dough covered to prevent drying as you work on the rest of the dough.

In a heavy-bottomed pot, heat vegetable oil to 350°F, ensuring there's enough oil for deep frying. Carefully add the dough circles in batches, frying them for 1-2 minutes per side until they turn golden brown and crispy. Use a slotted spoon to remove the shells and drain them on paper towels, allowing them to cool completely.

In a clean mixing bowl, combine ricotta cheese, powdered sugar, and vanilla extract. Mix using a hand mixer or whisk until the mixture is creamy and smooth, about 2-3 minutes. If desired, fold in some citrus zest for a fresh brightness.

Once the pastry shells are cool, fill a piping bag fitted with a round tip with the ricotta mixture. Carefully pipe the filling into each shell, filling about halfway to avoid overfilling, which could cause them to burst.

To finish off your Cannoli Bites, sprinkle crushed pistachios or mini chocolate chips over the filled shells for added flavor and texture. Serve them immediately for the best crunch and experience.