In a large mixing bowl, beat egg whites until frothy, gradually adding sugars until a shiny, stiff snow forms.

Add the vanilla sugar, coffee, whipped topping, and the egg yolks, and beat until the mixture is stiff.

Gently stir in the crushed chocolate-coated pretzels by hand.

Pour ice cream into a container and freeze until firm, at least 24 hours.

Place each type of chocolate into a plastic bag and soak in a bowl of boiling water until it melts.

Working with one bag at a time, cut off a tiny tip from the corner of the bag and drizzle on the overturned tacos, using a quick back-and-forth motion. Repeat with remaining chocolates; allow chocolate to harden.

Place two to three mini scoops of ice cream into each taco shell and sprinkle with a bit of crushed pretzels, if desired.

Serve with fresh fruit.