Grind the tsoureki in a food processor and place it in a large bowl together with the walnuts, cocoa, salt, and vanilla. Mix with a spatula (see note).

Place the dark chocolate and hazelnut praline in a heatproof bowl. Heat the cream until it begins to simmer. Pour the cream into the bowl with the chocolate. Let the mixture stand until the chocolate softens. Mix well until you have a velvety ganache.

Put the ganache in the bowl with the tsoureki. Add the sweetened milk and liqueur. Mix well.

Spread a large piece of plastic wrap on the counter. Transfer half of the karioaka mixture to the plastic wrap and roll it into a sausage shape. If the mixture is too wet and difficult to roll, leave it in the refrigerator for 10 minutes before continuing. Twist the ends of the plastic wrap and roll the sausage on the countertop to give it an even shape. Transfer the roll to the freezer. Repeat the process with the other half of the mixture.

Remove the rolls from the freezer after about 1 hour. Melt the chocolate for the coating in a double boiler together with the coconut oil. Cut the “salami” into 1 cm slices and dip them in the melted chocolate. Transfer to a rack or non-stick paper to dry. If desired, sprinkle with chocolate vermicelli or coarse salt while the chocolate is still liquid.