Heat the oven to 200C/180C fan/gas Lightly grease a 12 hole muffin tin.
Whisk the eggs with milk and season generously, add the grated cheese reserving some back for sprinkling on top later.
Line each of the holes with a rasher of bacon and a handful of spinach leaves and fill each one with the egg mix approximately two thirds full. Sprinkle the tops with the remaining cheese and top with chives.