3/4 cup butter
1/2 pound semi-sweet chocolate
1/2 cup sugar
3 tbsp cornstarch
4 whole eggs
4 egg yolks
Source: Mama Now Cooks Like This by Susan Mendelson (Whitecap)
Melt butter and chocolate in a saucepan over low heat.
Mix sugar and cornstarch together in a bowl. Crack eggs into another bowl and whisk yolks into whole eggs.
When chocolate has melted, remove from heat. Whisk in sugar-cornstarch mixture until blended. Add eggs and stir until smooth. Chill in the fridge overnight.
Preheat the oven to 400 F. Line a baking sheet with parchment paper.
Line 8 metal rings (you can use 1 1/2-inch deep tin cans with both ends opened) with a strip of parchment paper, or grease 1/2 cup ramekins. Set the rings on the baking sheet and brush generously with butter. Scoop chocolate filling into each one, filling them two-thirds full.
Bake in preheated oven for 12 to 15 minutes. Remove from oven. Slice a metal spatula under cakes and transfer to serving plates. Gently slide the rings off cakes and remove the parchment. Dust with icing sugar and serve immediately.