To a large saucepan of water add white vinegar, bring to simmer
To a large frypan gently melt the butter, when foamy add mushrooms and cherry tomatoes, tossing occasionally until cooked, remove from heat and keep warm.
Swirl simmering water until a whirlpool forms gently add eggs one at a time, this may need to be done in batches, poach for 5 minutes.
While the eggs are poaching gently wilt the spinach and slice the avocado