Preheat the oven to 425°F (220°C). Grease four muffin cups with butter and dust with flour.

In a mixing bowl, combine the chocolate chips and butter. Melt in the microwave in 30-second intervals, stirring until smooth.

Whisk in the powdered sugar until well combined. Add the eggs, egg yolks, and vanilla extract, whisking until smooth. Gently fold in the flour and salt until just combined.

Divide the batter evenly among the prepared muffin cups, filling each about 3/4 full.

Bake in the preheated oven for 12-14 minutes, until the edges are firm but the center is still soft.

Let the cakes cool for 1 minute, then carefully invert onto plates. Serve warm with a scoop of vanilla ice cream, drizzled with chocolate sauce and dusted with powdered sugar.