Take the thawed phyllo shells out of the packaging and place them on a baking sheet. Gently reshape any misshapen cups.

In a medium saucepan, combine the granulated sugar, butter, lemon juice, lemon zest, eggs, and egg yolks. Whisk together until well combined.

Place the saucepan over medium-low heat. Cook, stirring constantly, until the curd thickens enough to coat the back of a spoon, about 8-10 minutes.

For an ultra-smooth curd, pour it through a fine-mesh sieve into a clean bowl (optional).

Cover the bowl with plastic wrap, pressing it directly onto the surface of the curd. Refrigerate for at least 2 hours.

Once chilled, spoon or pipe the lemon curd into the phyllo cups, filling each cup nearly to the top.

Refrigerate the filled phyllo cups for at least 30 minutes before serving.

Before serving, dust with powdered sugar if desired. Garnish with lemon zest or fresh berry (optional).