Drain kale. Chop; press again gently in sieve to remove a bit more liquid. Put in a bowl.
Drain beef and mushrooms, capturing the liquid. Add the drained solids to a bowl.
To the beef and mushroom broth, add everything from the cornstarch down to the pepper. Whisk.
Zap in microwave on high for 1 minute. Whisk again, then zap for a final 2 more minutes.
Start heating oven to 225 C (425 F)
Stir the solids into the sauce. Heat to piping hot in the microwave -- about 5 minutes.
Spray a 2 litre (quart) baking dish with cooking spray.
Transfer the piping hot beef mixture into the baking dish.
Cover with 3 sheets of phyllo pastry, tucking in around the edges.
Spray the top lightly with cooking spray.
Bake for 7 to 10 minutes, or until top is nicely browned.
Serve hot.
Notes
You should have about 250 to 300 ml (around 8 to 10 oz / about 1 cup and a bit) of reserved beef and mushroom broth.Tip! You can make up the mixture ahead. Keep in fridge until ready to use, and bring to piping hot in microwave before putting in baking dish.You could also make a regular pie crust for this, adjusting the cooking temperature and time accordingly. Calories will go up.