Slightly beat 4 eggs. Add milk, water salt and sugar. Sift flour and add to liquid mixture. The batter should resemble thick whipping cream. Add a fifth egg if you need to make it thicker. Add butter. Let batter sit for half an hour or until it comes to room temperature and the bubbles settle.
Lightly butter a 7-inch non-stick pan and heat over low to medium heat. Pour 3 tbsp. of batter into the centre of the pan and swirl around the pan to make a thin pancake. Watch carefully and cook approximately 1 minute. When the crêpe is golden, flip it over and cook another 30 seconds. Remove to a plate for later. Repeat with the rest of the batter.
Place 2 tablespoons of the chocolate mixture (recipe follows)into the centre of one crêpe. Roll the crêpe, tucking in one end as you go.
Melt chocolate, butter and cream in the top of a double boiler. Mix to incorporate then place in a cool place and allow to cool completely. Sauté chestnuts in butter until golden. Mix chocolate filling thoroughly then stir in chestnuts and brandy.