Preheat the oven to 220°C (428°F). Grease six 175 ml ramekins with nonstick spray and place them on a baking sheet.
Combine white chocolate baking chips and cubed unsalted butter in a microwave-safe bowl. Microwave for 1 minute, stir, then continue in 15-second intervals, stirring after each, until smooth.
Stir in all-purpose flour, granulated sugar, lemon curd, lemon zest, and vanilla extract until just combined.
Gently mix in the whole eggs and egg yolks, ensuring the batter is smooth and fully incorporated without overmixing.
Divide the batter evenly among the prepared ramekins, filling each about two-thirds full.
Bake on the middle oven rack for 20 to 25 minutes, until surfaces are golden and spring back when touched.
Allow cakes to stand for 5 minutes. Run a knife tip around inside edges, invert onto plates, and let rest for 1 minute before slowly lifting ramekins off.
Dust tops with powdered sugar if desired and serve warm for a gooey lemon center.