Yield 24 raviolis / 3 per servings. A day ahead, soak dried porcini mushroom in cold water to cover and refrigerate overnight (it can be made a few days in advance). Drain porcini, squeeze and chop for the duxelles, and save porcini broth for the sauce.
Give button mushrooms a quick wash, drain and pat dry. Trim off bottoms and cut in four. In a food processor, give a few pulses until finely chopped but not pureed (process mushrooms in 3 batches). In a large hot oven proof skillet or rondo, add fat and saute duxelles and chopped porcini for 10 minutes on high heat. Add a pinch of salt and sift flour over (optional though); stir well. Meanwhile, preheat oven to 350ºF/180ºC. Finish cooking in the oven for 25 minutes; cool.
In a medium size frying pan, sweat shallots, crushed garlic until soft and translucent but not browning for about 5 min on low heat. Deglaze with port, bring to boil and reduce to dry on medium heat. Discard garlic and set aside.
Mix the warm duxelles with the shallot port mixture. Add parmesan and ricotta cheese. Season with salt, ground black pepper and white truffle oil. Transfer the finished duxelles in a clean container, wrap up and refrigerate for up to 3 days.
*Bouquet: parsley stems, thyme & black peppercorns. Bring to boil chicken and porcini stocks, and bouquet. Reduce volume by half. Drain and discard solids. Right before serving, reheat sauce and whisk in butter. Remove from heat and blend until foamy. Instead of butter, the sauce can be thicken with some heavy cream; cook down to a desired consistency. Readjust seasoning with salt and pepper to taste.
Lightly brush edge of wrapper with water or egg wash. Pipe out one ounce (30g) in center of the wrapper (one or 2 at the time), seal corners against each other from its base pressing out any trapped air. Repeat with remaining wrappers and filling, keeping wrappers covered as you work. Refrigerate ravioli for up to 3 days; covered.
Cook ravioli in 3 batches in a pot of salted boiling water for 2 to 3 minutes.
Serve 3 ravioli per plate. Pour some mushroom sauce. Garnish with finely chopped parsley and parmesan shavings, a few drops of extra virgin olive oil, and a pinch of fleur de sel and ground black pepper. Bon appétit!