Clean the two portobellos with a piece of paper towel and remove the stems. Cut the quarter avocado into thin slices or mash the flesh roughly with a fork. Place a large pan of water with a splash of vinegar on the heat and bring slowly to a boil.
Heat a grill pan on high heat and grill the portobellos on both sides until soft with dark grill marks. Meanwhile, create a gentle swirl in the hot water with a spoon. Gently crack the two organic eggs into it and poach for exactly three minutes until cooked.
Place the grilled portobellos gill-side up on the plates. Distribute the prepared avocado in the cavities of the warm mushrooms. Remove the poached eggs from the water with a slotted spoon, drain well and place one egg on each portobello.
Sprinkle a generous amount of chili flakes over the eggs. Serve immediately so the mushrooms and runny egg yolks are still nice and hot.