Put veal cutlets with plastic wrap or a freezer bag and gently pound it with a meat mallet or heavy pan.
Rinse sage, shake dry, pluck leaves and chop coarsely.
Rinse lemon in hot water and wipe dry. Peel the shell with a potato peeler thinly, then cut into very thin strips. (Alternatively, pull off with a zester into thin strips.)
Squeeze out lemon juice.
Peel the shallots and finely chop. Rinse spinach and spin dry.
Heat 1 tablespoon oil in an oven-proof pan over high heat. Cook veal cutlets until browned, about 1 minute on each side. Season with salt and pepper and transfer to a preheated oven at 100 °C (fan: 80°C, gas mark 1) (approximately 225°F/convection 175°F) until cooked through. Remove from oven; keep warm.
Wipe out the pan. Heat the remaining oil over medium heat and cook the shallots until translucent, stirring frequently, about 2 minutes. Add the spinach and cook until wilted, stirring frequently, 1-2 minutes. Season with salt and pepper and place on a warm plate.
Combine sage and lemon zest in the pan with 2 tablespoons lemon juice.
Add soy creamer, bring to a boil and season with salt and pepper.
Return veal cutlets along with the accumulated juices to the pan. Remove the meat from the pan, arrange on the spinach and serve with the sauce.