Preheat the oven to 180 °C/356 °F, no fan.
Cut the broccoli into florets and steam for 2-3 minutes.
Place the flour and diced butter in a bowl.
Rub the butter and flour with your fingers until you get a crumbly consistency, add the salt and water, shape into a ball, and chill for a few minutes.
Roll out the dough into a 0.5 cm (1/5th of an inch) thick sheet and transfer to a tart pan with a removable bottom (24-26 cm/9½-10 inch in diameter). Prick the dough with a fork.
Place the broccoli florets on top and then the chopped smoked salmon.
Whisk the eggs with the milk, salt and pepper and pour into the pan.
Grate the mozzarella and sprinkle over the tart.
Cover the tart with aluminum foil and bake for 45 minutes. Remove the foil for the last 15 minutes.
Serve the tart warm or cold! Enjoy!