In a large mixing bowl, combine all-purpose flour and salt, then cut in cold, cubed unsalted butter until the mixture resembles coarse crumbs. Gradually add ice water, mixing until the dough just comes together. Turn it onto a lightly floured surface, knead gently for a few seconds, wrap in plastic, and chill in the refrigerator for at least 30 minutes.

Preheat your oven to 375°F (190°C) while the dough chills.

In a bowl, whisk together eggs, crumbled feta cheese, and freshly chopped spinach. Season with black pepper and stir in optional herbs if desired.

Roll out the chilled pastry dough to about 1/8-inch thickness on a lightly floured surface. Cut out circles that fit into your tartlet pan.

Place the rolled-out dough circles into the greased tartlet pans and trim any excess dough. Spoon the spinach and feta filling into each pastry shell.

Bake for 20-25 minutes or until the crust is golden brown and the filling is set.

Allow the tartlets to cool in their pans for about 5 minutes before removing them. Garnish with halved cherry tomatoes or fresh herbs before serving.