Heat a large skillet over medium high heat. Add olive oil, then spinach. Season with salt and pepper and cook the spinach, stirring with tongs, until it has completely wilted – about 5 minutes. Remove from heat and set aside.
Melt the butter in a small saucepan over low heat. Remove from heat and stir in lemon zest and juice and chives. Season with salt and pepper and set aside.
Separate and toast the English muffins.
Poach the eggs (you can also soft boil them if you are not an egg-poaching type of person). While the eggs are cooking, place a quarter of the spinach on each muffin half, and place some salmon on the spinach. Top each portion with an egg. Divide the butter sauce by drizzling over each serving and garnish with chives or dill. Serve immediately.