First, melt the butter and dark chocolate together over low heat and stir until smooth. Set the mixture aside briefly so it is not too hot when you continue.

Whisk the eggs, egg yolks, and sugar together in a bowl. Sift in the pastry flour and mix until smooth, then add the salt.

Fold the chocolate-butter mixture into the batter and mix well until fully combined. Transfer the batter to a piping bag and let it firm up in the refrigerator for several hours.

Preheat the oven to 410 °F. Meanwhile, grease the inside of the metal serving rings with butter and dust them with flour, then place them on a baking sheet lined with parchment paper or a silicone baking mat.

Snip off the tip of the piping bag and fill the rings about two-thirds full with batter. Bake the moelleux for 8 to 10 minutes in the oven, so the outside is just set and the center stays soft.

Carefully remove the rings and serve the moelleux immediately while warm with vanilla ice cream and strawberries.