Festive eggs royale

To make the hollandaise sauce, place the vinegar and the juice of half a lemon in a small saucepan and bring to a simmer. Cook until reduced by about three-quarters, or until about 2 tablespoons remain. Add the reduced vinegar mixture to 4 egg yolks in a glass bowl, placed over a pan of simmering water, and whisk until thick and trebled in volume. Gradually add 250g melted butter, whisking constantly, until all the butter has been incorporated. Season to taste and keep warm.

Melt 15g butter over a medium-high heat in a large frying pan (ideally high-sided or a sauté pan). Fry the spinach with a pinch of salt for 2-3 minutes until wilted. Tip into a sieve and drain, then press to extract as much liquid as possible.

Rinse out the pan, then half-fill with just-boiled water from the kettle. Set over a medium low heat so that there are just occasional bubbles rising to the top. Crack one egg into a ramekin, then slip the egg into the water. Repeat with the remaining eggs, keeping them well apart. Poach for 3-4 minutes or until the whites are set but the yolks still soft.

Toast the muffin halves, then divide the pack of salmon and the spinach between them. Use a slotted spoon to lift the eggs from the water and pat dry with kitchen paper. Set each egg on top of the spinach, then drizzle over the hollandaise. Finish with 1 tsp salmon caviar, freshly ground black pepper and a squeeze of lemon juice.