Prepare the Avocado Mash: Halve the avocado, remove the stone, and scoop the flesh into a small bowl. Add the lime juice, a good pinch of salt, and a few grinds of black pepper. Using a fork, gently mash it, leaving some chunky texture. Don't over-mash it into a paste! The lime juice will help prevent it from browning. Set aside.

Toast the Bread: Place your sourdough slices in a toaster or under a hot grill. Toast them for 2-3 minutes per side, until they are golden brown and crisp on the outside but still have a slight chew in the middle. You can also toast them in a dry frying pan over medium heat.

Cook the Eggs: While the bread is toasting, heat the olive oil or butter in a non-stick frying pan over a medium-low heat. Once the pan is hot, crack the eggs directly into it. I find that a lower heat is key to getting perfectly cooked whites without the bottoms getting brown and crispy before the yolk is ready.

Fry to Perfection: Let the eggs cook gently for 3-4 minutes. For a runny yolk, you want the whites to be completely set and opaque. You can cover the pan with a lid for the last minute to help steam the top of the whites. For an expert guide on frying eggs, Serious Eats has a fantastic visual breakdown.

Assemble the Toast: Once the bread is toasted, place it on your plates. Spread the avocado mash generously over each slice, right to the edges.

Top and Serve: Carefully slide a fried egg onto each slice of avocado toast. Sprinkle over the red chilli flakes, a little more flaky sea salt, and the freshly chopped coriander or chives, if using. Serve immediately while everything is warm.