Make the lemon ganache base. Place the chopped white chocolate in a heatproof bowl. In a small saucepan, warm the cream and butter over medium heat until steaming and just starting to bubble at the edges. Pour over the white chocolate and let sit for 2 minutes.
Stir until smooth. Gently mix from the center outward until the chocolate melts and the mixture is glossy. If a few lumps remain, briefly set the bowl over a pot of barely simmering water and stir until smooth.
Add flavor. Stir in lemon zest, 2 tablespoons lemon juice, vanilla (if using), and a pinch of salt. Taste and add the extra tablespoon of lemon juice if you want a brighter punch. The mixture should be thick but pourable.
Chill to set. Cover the bowl and refrigerate for 2–3 hours, or until firm enough to scoop. You want a texture like soft clay.
Shape the eggs. Line a baking sheet with parchment. Scoop small portions (about 1 tablespoon each) and roll quickly into ovals with your palms to form egg shapes. If the mix is sticky, dust your hands lightly with powdered sugar or chill the mixture for another 15 minutes.
Freeze briefly. Place the shaped eggs in the freezer for 15–20 minutes. This helps them hold together during dipping and creates a clean coating.
Prepare the coating. Melt the coating chocolate or candy melts in short bursts in the microwave (50% power, stirring frequently) or over a double boiler. If it seems thick, stir in 1 teaspoon neutral oil to thin. Divide into bowls and tint with a drop or two of gel coloring for pretty pastel shades.
Dip the truffles. Working in batches, use a fork to dip each chilled egg into the coating. Tap the fork on the bowl’s edge to shake off excess. Slide the truffle onto parchment using a toothpick or another fork.
Decorate. While the coating is still wet, add sprinkles, a drizzle of contrasting color, or lines made by piping a bit of melted coating from a zip-top bag with a tiny snip.
Set and serve. Let the coating firm up at room temperature for 15–20 minutes, or chill for 5–10 minutes. Serve slightly cool or at room temperature for the creamiest center.
