pkg (397 g) frozen puff pastry, thawed
Tbsp Dijon mustard
tubs (475 g) ricotta cheese
cup grated Parmesan cheese
cup chopped fresh basil
tsp each salt and pepper
On lightly floured surface, roll out pastry to 16- x 12-inch rectangle. Fit into 13- x 9-inch metal cake pan, draping overhang over sides. Brush mustard over bottom; set aside.
In bowl, whisk together ricotta, eggs, Parmesan cheese, all but 2 tbsp of the basil, and half each of the salt and pepper. Scrape into pastry shell.
Thinly slice tomatoes; arrange over filling, overlapping slightly. Fold overhang over filling. Whisk egg yolk with 1 tbsp water; brush over pastry.
Bake in centre of 400°F oven until pastry is puffed and golden and filling is set, 35 minutes. Sprinkle with remaining basil, salt and pepper. (Make-ahead: Let cool for 30 minutes. Refrigerate until cold. Cover and refrigerate for up to 4 hours). Cut into squares.