Preheat oven to 425º F. Butter 4, 6 ounce ramekins and dust with cocoa powder
In the bowl of a stand mixer beat together eggs, egg yolks, sugar, salt and flour for 2-3 minutes until well combined and fluffy, scraping down the sides as needed.
In a microwave safe bowl, melt the butter. Add in the semi-sweet and milk chocolate chips and stir until the chocolate has melted.
Pour the chocolate into the egg mixture, make sure the chocolate isn't too hot, you don't want to scramble the eggs.
Mix until well combined. Pour evenly into the 4 prepared ramekins. Place the ramekins on a baking sheet and transfer to the oven.
Bake for 12-15 minutes, until the sides and top are baked, but the center is still soft.
Remove from the oven and while still warm invert onto a serving plate. Serve immediately.