Heat the oven to 200°C (180°C in a fan oven), 400°F, gas 6.
Fry the vegetables in the oil and season with salt and ground black pepper. Add the garlic and spread everything onto a baking tray. Roast for 15-20 minutes, turning occasionally. Turn the oven down to 180°C (160°C in a fan oven), 375°F, gas 5.
Place the pasty sheets next to each other and spread thinly with butter. Place them on top of each other and cut into quarters. Grease 4 tartlet dishes (approx. 11 cm ⌀) and place a piece of pastry in each one allowing the edge to spill over a little.
Mix together the tomatoes and the roasted vegetables, add the thyme and season with salt and ground black pepper. Place the mixture on top of the pastry and bake for 20-25 min.
Season the meat with salt and ground black pepper and fry in hot oil on all sides on a high heat. Roast for 5 min until medium rare.
To make the sabayon, mix together the garlic, rosemary, cream and stock and heat well until reduced to about half.
Beat the egg yolks and the vinegar in a bain marie and puree the cream mixture. Gradually add it to the egg yolk mixture, beating continuously until the mixture is foamy. Season with salt and ground black pepper.
Removed the tartlets from the oven, slice the meat and arrange on the ratatouille served with the sabayon.