I use the classic cream "Charlotte".
In a saucepan, mix egg, salt, vanilla, sugar. Stir and add the milk. I put it on the stove and cook until it thickens slightly on a lower-than-average heat. It took me about 10 minutes. In this cream, the egg-milk mass will be quite liquid, not the same as for custard.
And when the egg-milk mass has cooled, whisk the softened butter until fluffy and lightly whitened.
And then I connect both masses in several passes.
At the end I add cognac!!!
Whisk until smooth, and the cream is ready!!!