Prepare the filling; In a large pan, fry the sliced onion in olive oil for 3-4 minutes, add the sliced pepper and continue frying for another couple of minutes before adding the sliced mushrooms.
Stir and fry for 3 minutes, then add the red pepper flakes, wine, and baby spinach leaves. Cook over a medium heat, stirring, until the spinach has wilted and the liquid has reduced away.
Take pan off heat and leave to cool, then add the basil strips and the cream cheese, season with salt and pepper.
Lay 1 sheet of phyllo pastry onto a work surface and lightly brush with melted butter. Lay another sheet of phyllo on top and brush again with the butter. Do this with all sheets.
Place the cooled filling along the centre of the phyllo and bring each long side over to form a roll. Tuck ends in and turn the roll over, so the seam side goes underneath, place onto a baking sheet. Brush the top with melted butter and sprinkle with sesame seeds.
Place into a preheated oven, 400ºF and bake for 20 minutes, until pastry is brown and crispy.