In a large saucepan, heat 1tsp of the olive oil. Add the mushrooms, sage, onion, garlic, salt and pepper and sauté for 3-5 minutes or until soft. Then transfer to a bowl.
In a bowl or bag, toss the diced beef with the flour, lightly coating the beef.
In the same large saucepan, on medium to high heat, add the other 1tsp of olive oil with the steak. Allow the steak to brown, for ~8 minutes.
Add the mushroom mix back to the pan, along with the tomato paste, beef stock, red wine and kale. Bring to the boil, cover and then continue to cook for 2 1/2 hours.
Preheat an oven to 180 degrees. If using frozen filo pastry (like I did), allow it to thaw so that it is pliable.
Lightly brush your tin with olive oil and layer 1 sheet of filo pastry on the bottom, lightly brush the pastry with olive oil and repeat for 2 more sheets.
Spoon in the beef mixture and layer 1 sheet of pastry on top, lightly brushing it with olive oil. Repeat this for 3 more sheets (I curl up the last sheet to give the top some texture)
Brush the tops with the egg, and sprinkle on the sesame seeds before baking for 25 minutes, or until golden on top