Preheat oven to 180⁰C.
Blanch the broccoli florettes in boiling water for 2 minutes then plunge into cold water and drain (sit on kitchen paper while they’re waiting to be used).
Grease a lasagne tin (20cm x 24cm).
Unroll pastry and with a rolling pin and roll the shortest length a little wider to fit the tin.
Place the pastry sheet over the tin, press into the corners then trim the excess pastry with a knife.
Put ¾ of the cheese in the base of the pastry case.
Pat the tomato slices dry and then lay over the cheese followed by the broccoli.
Top with remaining grated cheese.
Whisk together the egg, milk, onion, salt and pepper.
Pour over the broccoli and fold down the sides of the pastry.
Bake on the bottom shelf of the oven for 42 – 45 minutes until golden and pastry cooked through.