Blend the spinach with the water, pour it into a bowl and dissolve the yeast in it.
Gently squeeze the liquid out of the courgette, and add the courgette to the spinach water along with the linseeds, egg and honey.
Mix the plain flour, wholemeal flour and salt, and add it a little at a time.Mix the dough in the stand mixer until all the flour is well worked into the dough - adding it a little at a time.
Add the butter in cubes, and knead the dough thoroughly until it comes away from the sides of the bowl. This takes 5-8 minutes depending on the power of your mixer.
Grease your hands with a little oil, shape the dough into a ball, and place it back in the bowl.Cover with cling film and a tea towel, and leave the dough to rise at room temperature for 1 1/2 hours.
Knock the air out of the dough, divide it into 18 equal pieces, about 80 g each, and shape them into rolls. Build some tension in the dough by folding the underside in over itself, then roll the rolls into smooth rounds. If the dough is sticky, you can grease your hands with a little oil; avoid using more flour as far as possible.
Leave the rolls to prove on a baking tray lined with baking paper, cover with a tea towel and leave them for 30 minutes.
Brush the rolls with milk, and bake them in a preheated conventional oven (top and bottom heat) at 225°C for about 12 minutes.
Leave the rolls to cool before packing them into tightly sealed bags.