Mix the warm milk, sugar and yeast together. Allow to froth up for five minutes before adding the flour, butter and eggs.
Knead on a floured board to make a smooth dough. Allow to puff up before pushing back to let the air out.
Roll out the dough to around 1cm thickness, in a rough rectangle shape.
Meanwhile, make the philly cheesesteak mix - in a wide heavy frying pan brown the meat, in batches if necessary. Add a little more oil to the pan and fry the peppers and onion until soft, then re add the meat and season with salt, pepper and garlic powder.
Cut the rectangle of dough into equal roughly 10cm strips.
Spread the cheesesteak filling over the strips and sprinkle with mozzarella.
Roll them up like a snowball, being careful - it can get quite hard to handle at this stage!
Press into a lined cake tin and bake for around 1 hour, until cooked through and well risen.
Meanwhile, make the cheese sauce - heat the butter until foaming and add the flour. Cook out for a minute, then gradually pour in the milk. Allow to cool slightly then add the cheese, adding more as needed to thicken the sauce.
Pour the cheese sauce over the spiral and serve in slices like a delicious cheesy cake.