Heat another frying pan, or a griddle pan, until hot, and heat oven to 140C/120C fan/gas 2. Now assemble the burritos. Warm a wrap for 10 secs on the hot pan (keep the pan hot, you’ll need to use it again). Pile roughly a sixth of the rice mixture onto the centre of the wrap. Top with a little avocado and some cheese, then brush beaten egg around the edge. Fold the ends over the filling, then fold in the sides, like an envelope. Flatten a little to a parcel, then place, seam-side down, in the hot pan. Cook for 2 mins until the underside has sealed shut and is toasted a golden brown, flip over and cook for a few mins more.