Preheat the oven to 375°F/190°C.
Wrap garlic cloves in foil and bake until tender (package will feel soft when pressed), about 25 minutes. When cool enough to handle, mash cloves in a small bowl until smooth.
Preheat the broiler to medium-high. Brush the veal steak with mustard and place lemon slice on top of the steak. Broil the veal until cooked through, about 2 minutes. Transfer the veal steak to a plate and cover loosely with foil to keep warm.
Pour chicken stock and lemon juice into a small saucepan and whisk in the cornstarch. Add the roasted garlic and bring to a boil over medium heat. Continue boiling until the sauce is slightly thickened, about 1 minute. Spoon the lemon-garlic sauce over veal steak.
Bring about an inch of salted water to a boil in a large skillet. Add asparagus in one layer. Cook until tender, about 6 minutes. Drain asparagus and transfer to a plate holding the steak.
Add cherry tomatoes. Season to taste and serve.