Beat the egg with a mixer until smooth. Pour in milk and whisk again, then add sugar and vanilla. Beat until smooth.
Put on a slow fire and cook constantly stirring after boiling for 2-3 minutes. The cream should be a little thicker.
Cover the cooked cream with cling film so that it comes into contact with the surface and completely cool.
Beat soft butter with a mixer until lush. Add cream to the oil in small portions and beat well after each addition.
The cream is homogeneous, gentle and airy. Before use, you can refrigerate for 20 minutes.