Norman cuisine
In Normandy they use reduced stock made from veal bones, but you could use a homemade or commercial veal stock to simplify this recipe. 

*The kidneys are served with crispy potatoes. Simply peel the potatoes and slice them paper thin, lengthwise, on a mandolin. Dip in melted butter and place on a baking sheet. Put under a very hot broiler and remove once crisp and golden. Homemade potato chips! 

1. Heat the oil in a cast iron cocotte or Dutch oven; add the whole kidneys; brown on all sides and finish by cooking at high heat for 8 minutes. Remove and keep warm.
2. Degrease the pot; sweat the shallots gently without browning; add the vinegar and calvados. Reduce; add the veal stock, then the crème fraîche. Thicken, strain and keep warm in a double boiler.
3. Cook the potatoes as described above; cook the snow peas in salted water. Refresh in ice water. Just before serving reheat in butter.
4. Brush the mushrooms; place into a hot skillet and let them exude their water. Sauté in oil and butter. Keep hot in the sauce.
5. Halve the kidneys; place on plates; garnish with the potatoes and snow peas. Spoon on the mushroom calvados sauce.