For the pastry:
1 lb cold unsalted butter
3 1/2 cups all-purpose flour
1 3/4 teaspoons salt
1 cup cold water
For the filling:
2 or 3 tablespoons of Dijon mustard
1 cup of shredded Emmental cheese (or Gruyère)
12-16 cherry tomatoes, cut in half
salt and pepper
2 tablespoons olive oil
- Cut the butter into 1/2-inch cubes. Refrigerate until the cubes are chilled and firm.
- In a large bowl, combine flour and salt. Add butter and toss with your fingertips until butter is coated with flour. Add all but about 2 tablespoons of cold water. Mix with a pastry blender or a table fork until an evenly moist but still rough dough forms. Add additional water, if necessary, as you mix the dough if it is not moist enough to hold together when pressed into a ball.
- Cover dough tightly with plastic wrap. Refrigerate until butter in dough is firm but not brittle, about 20 minutes. Turn dough out onto a lightly floured work surface or marble. Roll it into a 12×30-inch rectangle approximately 1/2 inch thick.
- Fold dough in thirds like a letter (this is the first of four 3-folds). Turn dough 90 degrees. Roll dough out again to a rectangle as described above and fold once more (this is the second of four 3-folds). Wrap the dough tightly in plastic wrap and refrigerate for 30 minutes. Remove dough from refrigerator and, working quickly, continue rolling and folding dough for the third and fourth 3-folds as described above, chilling the dough in between each of these folds for 30 minutes at a time.
- After completing the final 3-fold, wrap the dough in plastic wrap and allow it to firm under refrigeration for at least 1 hour before using. The dough will last up to 1 week in the refrigerator or may be frozen for up to 2 months.
- Preheat the oven to 425°F. Divide the pastry into two parts. Roll out each piece until it is a rectangle about 3/8” thick. Spread a thin layer of Dijon mustard over the pastry, leaving a 1/2” border around the edges. Sprinkle the cheese over and then the tomatoes. Sprinkle with salt and olive oil. Bake the tart at 425°F for 20 minutes, until browned and puffy.