I bought a special baking attachment for Eggnog "mountain peaks" in a specialized baking supplies shop, so I had to try it since everyone is already praising it so much. And especially my father, who loves them and doesn't want to share them :D
Mix vanilla pudding, cocoa, sugar and water in a small saucepan. Put it on a moderate fire, stir constantly and cook a thick porridge. Set aside and immediately add the chocolate (1.7 oz), broken into pieces. Dissolve it by stirring. Be careful not to burn the mass - cook for only about 4 minutes. Let it cool completely. (You can also prepare the mass in the evening beforehand and work with it the next day. I cooked the mass in the morning and made the "mountain peaks" in the afternoon).
Beat the fat, add the chocolate mass and thoroughly beat into the smooth cream with a mixer. Put the mass in the fridge for a while, then transfer it to a plastic bag. Put the baking decorating tip (the attachment) in the plastic bag so that the hole of the tip is outside and not inside the plastic bag. If it's inside, you won't be able to get the cream through it, so watch out for that.
Make sure that you have the mass properly whipped so that it is free of lumps, because it will pay off when you spray the cream.
Using a plastic bag with a special tip, spray the cooled cream onto the round cookies (keep a little cream for the end, you will need it for the top), which you have coated with chocolate so that they do not soak after being filled with eggnog.
Eggnog mass: I thickened the eggnog with dry powdered milk - the exact amount of the instant milk cannot be given as it depends on the density of the eggnog itself.
Fill the tips ("mountain peaks") with eggnog and close the top with a decorative baking tip.
Put the eggnog "mountain peaks" in the fridge to solidify properly and then dip them in the melted chocolate glaze. Do not forget that the cream must be sufficiently cooled in order for you to be able to work with it.