Roast the diced portobello, shiitake, king oyster.
In a 375°(190°C) oven, roast 1 cup of diced portobello, reserved diced shiitake, and reserved diced king oyster with a drizzle of olive oil and salt and pepper to taste. Place the mushrooms in one even layer to roast evenly. Roast for about 10 minutes, or until mushrooms are aromatic, have shriveled up and browned. Remove from oven and blend ⅔ of the mixture in a food processor until mushrooms form a paste-like consistency. You can add some olive oil to help blend if the mixture is too thick. Reserve the remaining ⅓ of roasted mushrooms and set aside.
Cook down rice and oats.
In a pot, combine rice and oats with 2 cups of water to begin with. Cook over medium heat until mixture begins to bubble and lower heat to low-medium. Continue cooking until water has evaporated. Add another cup of water and mix. Continue this process (almost like making a risotto) until the rice and oats have cooked down and form the softness and consistency of your liking. Continue tasting as you go. Add the blended mushroom mixture along with the rest of the roasted mushrooms to the porridge. Salt and pepper to taste. Turn the heat to low and allow the mushroom mixture to integrate into the porridge for another 5 minutes.
Marinate king oyster mushrooms.
While the porridge is cooking, marinate the sliced king oyster mushrooms in a mixture of soy sauce, water, and balsamic vinegar. Before marinating, score the one side of the mushrooms by slicing shallow lines across the mushroom about ¼” apart. Be careful not to score too deeply to avoid cutting the mushroom apart. Turn the mushroom around and score more lines perpendicular to the lines you’ve already made, creating a grid pattern. Scoring will allow the marinade to soak deeper into the mushroom, which also means more flavour. Combine the soy, water and vinegar in a bowl and pour over the scored mushrooms onto a shallow dish. Allow to marinate for at least 10-15 minutes before grilling.
When the mushrooms are done marinating, warm grill up to 375°(190°C), and place the mushrooms scored side down onto the grill. Grill for 2-4 minutes at most and remove from grill. You’ll only need to grill on one side to create the grill marks. Since the mushrooms are sliced thin, it won’t take long to cook through and cooking on both sides may lead to overcooking.
Fry shiitake mushrooms.
In another pot or wok, heat up about ¼ cup of peanut oil or any oil with a high smoke point over medium heat. When the oil begins to shimmer, drop your very thinly sliced shiitake mushrooms into the oil and fry. The mushrooms should sizzle when you drop it into the hot oil. Continue to fry until the mushrooms have shriveled up about half the size and become a darker shade of brown. Keep a close watch. The mushrooms can burn easily if you don’t. Remove mushrooms when they’ve become crisp. Transfer onto a plate lined with paper towels and blot the mushrooms well to get all the excess oil out. You can also wrap the mushrooms in paper towels and put a weight on it like a book with canned beans on top to squeeze the oil out. This will result in crispier mushrooms.
Get a small pot and fill with water. Bring the water to a boil over medium heat and add a generous heap of salt. Add the vinegar as well and stir. Once the water just begins to boil, turn the heat down to low-medium. With a whisk, begin swirling water in a circular motion to create a whirlpool. Swirl vigorously so that the whirlpool swirls quickly on it’s own.
Crack your eggs in a ramekin or small bowl, one individual egg per bowl. While the whirlpool is still swirling, drop the egg very carefully and slowly into the center of the whirlpool. Let the egg poach in the pot for 5-10 minutes, or until the egg white has solidified. Use a slotted spoon to remove the egg. If you are serving immediately, put the poached eggs on a paper towel and blot to take away excess water. If you are serving later, you can prepare a bowl of water with ice in it to put the poached eggs in and set aside.
Finish porridge with pecorino.
When the porridge is at the right consistency and cooked through, finish it with ¼ cup grated pecorino. Mix in well and taste. If you feel that it could use more cheese, add more grated pecorino as desired. The cheese will provide some salt to the porridge so salt and pepper to taste after you’ve mixed in the pecorino.
Assemble, garnish and serve.
Ladle the porridge into serving bowls, spoon the poached egg onto the center. Lay grilled mushrooms on one side of the egg with the grill marks facing up. Lay shiitake chips on other side of egg. Drizzle truffle oil over porridge and mushrooms and grate some more pecorino over the dish. Finish with a pinch of salt if desired and serve. Congrats! You just made mushroom porridge.