In a large bowl, add all the ingredients except the baking soda, orange juice, and flour.

Next, dissolve the baking soda in the orange juice and add it to the mixture.

Add the flour gently, mixing just until combined so the oil doesn't separate.

Make the syrup by boiling all the syrup ingredients until the sugar dissolves. The melomakarona should be cool and the syrup hot. Dip each cookie for 3 seconds on each side.

Melt the chocolate bars in a double boiler and add 2 tablespoons of sunflower oil.

Dip each melomakarono in the chocolate, then place on parchment paper or a rack. Sprinkle with chopped walnuts if desired.

Let them cool until the chocolate sets.