Bring a medium pot of water to a gentle simmer and add white vinegar.
Crack each egg into a small bowl, create a gentle whirlpool in the water, and slide in eggs one at a time.
Poach eggs for 2½ to 3 minutes until whites are set but yolks remain soft.
Remove eggs with a slotted spoon, drain on paper towels, and chill in the fridge for 10 to 15 minutes.
Prepare three bowls with flour, beaten egg, and panko crumbs for coating.
Roll each chilled poached egg gently in flour, dip into beaten egg, then coat thoroughly with panko crumbs.
Heat neutral oil in a small pan to 350°F (175°C).
Carefully fry each coated egg for 30 to 60 seconds until golden and crispy, then drain on paper towels.
Lightly sprinkle fried eggs with sea salt flakes.
Toast bread slices and mash avocado with a pinch of salt.
Spread mashed avocado over toast, place crispy panko poached eggs on top, then sprinkle with crumbled feta cheese and chili flakes.