Melt chocolate with butter over a bain marie and mix very well until incorporated.
Whip yolks with 50gr sugar until ribbon stage pale yellow, and set a side.
Whip whites with sugar 44gr until soft peaks.
Fold yolk mixture with chocolate until incorporated with a spatula gently.
Then fold whites to chocolate mixture. Start with a small amount of whites. Use a whisk to fold into the chocolate gently folding from bottom of the bowl to the top until incorporated.
Ladle the mousse into 4ea 8oz ramekins or one big sharing bowl.
Let mixture set for 4 hours to set in refrigerator before serving with strawberries.