Blend the spinach with the water, pour it into the mixing bowl and dissolve the yeast in it.
Add the honey, egg, linseeds and grated carrot. Squeeze a little of the liquid out of the carrots first, so the dough does not become too wet.
Mix the plain flour, wholemeal flour and salt, and add it a little at a time. Mix the dough in a stand mixer until all the flour is thoroughly worked into the dough – keep 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.
Rub your hands with a little oil, shape the dough into a ball and return it to 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 of about 80 g each, and shape them into rolls. Build tension in the dough by folding the edges into the centre underneath, then roll the rolls into smooth, round balls. If the dough is sticky, rub your hands with a little oil and avoid using more flour as far as possible.
Leave the rolls to prove a second time on a baking tray lined with baking parchment: 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 in airtight bags.