Heat 1 tsp olive oil in a large frying pan. Brush away any dirt on the mushrooms. Season and place them, stalk-side down, in the pan. Cook for 3 minutes, turn, then cook for a further 5 minutes. Place on a tray and transfer to a warm oven.
Halve the tomatoes and remove the green 'eye' with a small, sharp knife. Season, then place them cut-side down in the pan and cook without moving for 3 minutes. Gently turn over and season again. Cook for a further 2 minutes until tender, but still holding their shape. Transfer to the tray in the oven.
Lastly, crack the eggs straight into the pan. If it starts to spit, turn down the heat slightly. Cook to your preferred stage, season and gently remove. While the eggs cook, pierce the bag of spinach several times and place on a non-metallic plate. Cook in the microwave according to packet instructions and allow to stand for 1 minute. Transfer to a large bowl and squeeze out any excess liquid.
Once all the ingredients are cooked, serve on warm plates and divide the avocado between the portions. Enjoy with your choice of condiments.