Preheat oven to 325 F.
Cut 6.5 tbsp butter in small pieces. Put the butter and water in a pan. Bring to boil over a medium heat. Add the flour and reduce the heat. Stir using a wooden spoon until the mixture is homogeneous, about 2-3 minutes.
Take the pan out of the stove. Add the eggs one by one, stirring continuously until the mixture is homogeneous. Using a spoon, make small elongated éclairs, and place them on a parchment-lined baking pan.
Bake the éclairs until golden-brown. *You must not open the oven door at all during the first 15-20 minutes!* Usually, the éclairs are done in 35-40 minutes. Take out of oven and allow to cool down.
While the éclairs are baking, put the eggs and the sugar for the pastry cream in a pan. Place pan on the counter (*not* on the stove). Mix until well combined. Add flour in stages, stirring well after each added tbsp. Add the milk in stages as well, stirring continuously until the mixture is homogeneous. Put the pan on the stove over a medium heat, stirring continuously. The mixture will start to thicken. Once the cream has thickened, cook for another 1-2 minutes, stirring repeatedly.
Take the pan out of the stove. Cut 4tbsp butter in small pieces and add to cream, stirring continuously until well combined. Lastly, add the vanilla extract and mix well. Allow cream to cool slightly.
Cut the éclairs in half and fill them with pastry cream.
Serve the éclairs with whipped cream, berries and/or chocolate sauce, as per your preferences.