In a small saucepan, warm the half and half with the white chocolate and sugar over low heat. Stir gently until the white chocolate is melted, then remove from the heat.

In a separate bowl, whisk the egg yolks. Gradually add the warm half and half mixture to them, stirring gently with the whisk. Add the Kirsch and vanilla extract if using.

Preheat the oven to 350 degrees F. (175 Celsius).

Set four ounce (125 ml) ramekins or six ounce (150 ml) custard cups in a baking pan with high sides. Add warm water to the larger pan, so that the water reaches half way up the outside of the custard cups, creating a water bath. Cover the pan with foil and bake for about 40 minutes, or until the custards appear to be slightly jiggly.

Remove the custards from the water bath and cool on a wire rack.

Serve slightly warm, or at room temperature, topped with the fresh raspberries.