Prepare Italian Meringues.
Prepare Coffee Zabaglione.
Cream butter in a large bowl until pale and fluffy.
Gradually add cooled zabaglione to butter, beating vigorously after each addition.
Refrigerate 2 to 3 minutes to stiffen slightly.
On a large round platter, arrange about 8 meringues close together in a circle.
Put zabaglione mixture into a pastry bag fitted with a medium star tube.
Pipe rosettes between meringues.
Arrange another layer of meringues over the first, forming a smaller circle.
Pipe rosettes of zabaglione mixture between meringues.
Repeat layers using remaining meringues and most of zabaglione mixture to make a cone-shape mound.
Decorate cake with candied violets and remaining zabaglione mixture.
Refrigerate overnight.
Italian Meringues: Preheat oven to 275F (135C).
Butter and flour 2 cookie sheets.
In a large bowl, beat egg whites until stiff.
Beat in 6 tablespoons sugar, 1 tablespoon at a time.
Beat in vanilla and vinegar.
Add remaining sugar, beating until egg whites are very stiff and shiny.
Put egg white mixture into a pastry bag fitted with a medium star tube.
Pipe mixture in small mounds onto prepared cookie sheets or shape into mounds using 2 spoons.
Bake 1 hour.
Turn off oven.
Leave meringues in oven overnight with door closed.
Store meringues in an airtight container.
Meringues can be stored several weeks.
Coffee Zabaglione: In a large bowl or the top part of a double boiler, beat egg yolks and sugar until pale and thick.
Set bowl or top part of double boiler over simmering water; do not let water boil.
Gradually add coffee, beating constantly.
Continue beating until zabaglione has doubled in volume and is soft and fluffy, 4 to 6 minutes.
Remove from heat and set pan or bowl over a bowl full of ice water.
Stir with a whisk until mixture is cool.