Put 1/2 the sugar to caramelize and gradually dilute it with the hot milk.
Add the ground walnuts.
Separately, beat the butter with the powdered sugar and add it spoon by spoon to the walnut mixture.
Beat the egg whites carefully with a mixer, add the remaining sugar gradually.
Put the container with whites on the stove, beat in a water bath until it turns to a thick snowy mixture.
Pour the lemon juice in very slowly and beat. Remove from the stove and leave to cool completely in the water.
Then combine the 2 creams - the egg white with the walnut one. Use the cream when preparing cakes.