For the dough: in a bowl pour the flour and add the cold butter cut into cubes. Mix by hand (better than a food processor). Make a hole in the middle and add salt, water and egg yolk. Turn the dough out onto your work surface and gather it into a ball. Cover with plastic wrap and set in the fridge for at least 30 minutes
Filling : whisk together brousse and cottage cheese, add chives and season to taste. Set in the fridge.
Preheat the oven on 400F
Roll out the pastry on a floured surface. Cut out 4 discs and gently lay in each tart pan. With the tines of a fork, prick the bottom of the dough. Bake the tartlets for 20 minutes until the crust is dry and lightly browned. Let cool.
In the meantime, cut the radishes into thing slices.
Spread the cheese filling on the tartlets. Top with slices of radish. Add some chives and serve with a nice salad.