Bring a large pan of water to the boil, then lower the heat to a simmer. Swirl the water to create a whirlpool, then add the eggs and poach for 4-6 minutes, depending on how runny you want the yolks.
Meanwhile, toast the muffins. Top with a little spinach and slices of the salmon.
To serve, remove the poached eggs with a slotted spoon and place on top of the salmon. Dollop with the hollandaise sauce and garnish with the chives.