Add the milk, salt, honey, and washed spinach leaves into a blender or a container suitable for an immersion blender. Add the egg at the end.
Place the spinach purée into a large mixing bowl, then add the two kinds of flour, the yeast, and the softened butter.
Knead the dough. A food processor with dough hooks would be perfect here, but you can use your hands as well.
Sprinkle 2 tsp of vegetable oil into the bowl and rub it around using the dough. Let the dough proof for at least two hours, covering the bowl with plastic wrap to prevent drying out.
Once the dough has roughly doubled in size, knead it again.
If you have two smaller loaf pans, there will be enough dough for two loaves of bread. A large loaf is also possible.
Preheat the oven to 350°F. Bake the bread for 30 minutes.
When the crust is nice and golden brown, take it out of the oven. Cut into lukewarm slices and enjoy!
