Preheat oven to 390 F. To prepare the dough brewing (that's how we call it in Russian) you need to bring water to a boil in a small saucepan. Add the butter and salt, stir until melted. Reduce heat and gradually sieving flour into a saucepan, stirring constantly. The dough should have no lumps. Remove it from heat. Beat the eggs lightly with a fork, add small portions in a dough, mixing well. Cover the baking shit with parchment paper. Put a tablespoon of dough at a distance of approximately 5 cm from each other. Bake 30 minutes in the oven until golden brown. Turn off the oven, but do not open the door for 10 more minutes, so the dough does not fall. Do not open the door during eclairs are baked,  too. Then transfer to a wire rack and let cool 15 minutes. Meanwhile, prepare the cream. Beat mascarpone with a cold cream, sugar and vanilla essence until creamy. Cut the top of the eclairs with a knife. Using a pastry bag, fill the void with a cream, put the fruit and cover with a cut top. For the icing, melt the butter in a saucepan, add cocoa, sugar and milk, so the glaze has become quite liquid. Stir well and remove from heat. Pour the finished eclairs with chocolate icing.