Melt the butter in a pressure cooker, brown the roast on all sides, then add the chopped onion, salt and pepper.
Brown the mushrooms and the garlic clove in the oil over a high heat, then after a few minutes add the potatoes, mix and season with salt and pepper.
Rub the roast all over with the cut slice of garlic; discard the garlic. Season the meat with kosher salt and freshly ground black pepper.
Mix the veal stock, herbs, basil, white wine and 1 glass of water in a bowl. Pour this mixture into the casserole dish, along with the washed and quartered mushrooms and stir.
Close the casserole dish and leave to whisper for about 40 minutes .
Pour the mushroom and onion mixture over roast.
keep the mushrooms and onion mixture moist. The internal temperature of the veal should be about 145 F for medium rare, 160 F for medium, or 170 F for well done.
