Start by preheating your oven to 375°F. While the oven heats, bring your butter and egg to room temperature (around 70°F) if they aren't already—this ensures smooth, even mixing and better texture in the final cookies. Sift the powdered sugar to remove any lumps, grate your lemon zest fresh, and chop the white chocolate into small, uniform pieces for even melting later. Having everything prepped and ready will make the dough-making process smooth and efficient.

In a large mixing bowl, beat together the room-temperature butter, sifted powdered sugar, and salt for 2-3 minutes until the mixture is light and fluffy—this aerates the dough and creates a tender cookie. Add the room-temperature egg, lemon zest, and vanilla extract, then beat for another minute until fully combined and smooth. Finally, add the flour and mix on low speed just until the dough comes together; I find it's important not to overmix at this stage, as overworking the dough can make the cookies tough rather than delicate. The dough should be smooth and pipeable.

Fill your cookie press with the dough from Step 2 and attach the ribbon disk. Press long, continuous dough strips onto ungreased cookie sheets, spacing them about 1 inch apart. While the strips are still on the warm sheets, use a sharp knife or kitchen shears to cut each strip into 1-inch lengths—cutting while slightly warm makes this much cleaner than trying to cut cold, fragile cookies. If the dough becomes too soft to cut cleanly, let the sheets rest in the refrigerator for 5 minutes before continuing.

Bake the cookie ribbons at 375°F for 7-9 minutes, until the edges are just beginning to brown but the centers remain pale—you want delicate, tender cookies, not crispy ones. Remove from the oven and let them cool on the baking sheets for 2-3 minutes until they're firm enough to handle but still slightly warm, then transfer to a wire rack to cool completely. I like to bake in batches so you can work with one tray while the next bakes, keeping your workflow smooth.

Place the chopped white chocolate in a heatproof bowl and set it over a pot of gently simmering water (a double boiler setup), stirring occasionally until smooth and melted. Once the cookies from Step 4 are completely cooled, spread a thin layer of melted white chocolate on the flat bottom of one cookie, then press the flat bottom of another cookie on top to create a sandwich. Repeat until all cookies are paired, then place them on a parchment-lined baking sheet and refrigerate for about 5 minutes until the chocolate is completely set and the sandwich holds together.

Reheat the white chocolate slightly if it has become too thick (it should be thin enough to dip into). Working with one sandwich cookie at a time, dip a corner into the melted chocolate, then immediately dip that chocolate-covered corner into the assorted nonpareils for a colorful garnish. Place the decorated cookies on a fresh piece of waxed paper and let them sit at room temperature until the chocolate is completely set, about 10-15 minutes. This final decoration step adds a festive, professional touch to these elegant treats.