Whisk together the chestnut flour, egg and water. Allow the mixture to sit for 10-15minutes while you make the filling.
Mix together the mascarpone and honey (and rosewater if using) in a small bowl and set aside.
Melt a small knob of butter (no more than ¼tbsp) or oil in a small skillet/frying pan over a medium heat and once the pan is fairly hot, pour a little of the pancake mixture into the pan and swirl around to form a thin layer. If you end up with gaps, fill with a little extra batter immediately while mixture still semi-liquid so it joins.
Cook for a couple minutes on each side - you should see it is ready on the first side as it starts to curl on the edges.
Once they are cooked, set aside and cover with a clean dishtowel to keep warm while you cook the rest.
Serve with a spoonful of the mascarpone mixture spread inside each crepe - I suggest rolling them up.