Preheat your oven to 425 F.

Put the minced garlic on a cutting board and sprinkle some course sea salt onto it. Using the flat of your knife, crush the garlic into a paste. Scrape the paste into a bowl and add the lemon zest, rosemary and spinach. Add a splash of extra virgin olive oil and mix to combine.

Lay the tenderloins onto a foil-lined baking tray so that the skinny end of one is against the fat end of the other. Make sure the loins are touching. Spoon the stuffing where the two loins meet. Carefully truss the loins together (I found 6 evenly spaced trusses worked pretty well). If any filling spills out, just push it back into the seam.

Rub the loins with a little olive oil, then season with salt and freshly cracked black pepper. Put the tray into the oven and bake for 35 minutes, or until a thermometer inserted into the thickest parts of the loins reads 135 F to 140 F.

Pull the tray from the oven and squeeze the juice from half a lemon onto it. Put it back in the oven for 1 to 2 minutes at a high broil, to brown the surface.

Pull the tray from the oven. Baste the meat with any tray juices, then let it rest for 5 minutes before carving into thick slices. Serve with a drizzle of the best quality balsamic vinegar you can afford.