½ cup (1 stick) unsalted butter, plus additional for preparing the ramekins
5 ounces white chocolate, chopped
2/3 cup all-purpose flour
½ cup confectioners' sugar, plus additional for dusting
½ cup lemon curd
Zest of 1 lemon
1 teaspoon vanilla extract
4 large eggs
4 large egg yolks
Preheat the oven to 425 F, and grease eight 6-ounce ramekins with butter. Place them on a baking sheet.
In a large microwave-safe bowl, combine the butter and white chocolate, and heat for 1 minute on 50% power. Stir the mixture, and then microwave in 20-second increments on 50% power, stirring in-between, until the chocolate is completely melted and the mixture is smooth.
Whisk the flour into the butter-and-chocolate mixture, then stir in the confectioners' sugar, lemon curd, lemon zest and vanilla until well-combined. Beat in the eggs and egg yolks until incorporated.
Spoon the batter into the buttered ramekins, dividing it equally.
Bake for 15-20 minutes, until the edges of the cakes are set. Remove the cakes from the oven, and let them rest for about 5 minutes.
Run a knife around the edge of the cakes to loosen them, and then carefully invert each one onto a serving plate. Sprinkle with confectioners' sugar, and serve warm.