Bring 1 cup Marsala, chicken broth, gelatin, and porcini mushrooms to boil in small saucepan. Reduce to medium-low and simmer until reduced by half, 15 mins or so.

Meanwhile, cut chicken into 3 square pieces, sprinkle with salt, pepper and flour. Pound between sheets of plastic wrap to 1/2-inch thickness. Set aside.

Strain Marsala/broth reduction, pressing on solids to extract as much liquid as possible; discard solids. Set aside.

Dredge cutlets in flour, shaking gently to remove excess. Place on plate. Heat 2 tablespoons oil in 12-inch skillet over medium-high heat until smoking. Place cutlets in skillet and lower heat to medium. Cook until golden brown on 1 side, 2 to 3 minutes. Flip and cook until golden brown on second side, 2 to 3 minutes. Set aside.

Return now-empty skillet to medium-low heat and add pancetta. Cook, stirring occasionally, scraping pan bottom to loosen browned bits, until pancetta is brown and crisp, about 4 minutes. Add cremini mushrooms and increase heat to medium-high. Cook, stirring occasionally and scraping pan bottom, until liquid released by mushrooms evaporates and mushrooms begin to brown, about 8 minutes. Using slotted spoon, transfer mushrooms and pancetta to bowl. Add remaining 1 teaspoon oil and shallot to skillet and cook until softened, 1 minute. Add tomato paste and garlic and cook until fragrant, 30 seconds. Add reduced Marsala mixture, remaining 1/8 cup Marsala, lemon juice, and oregano and bring to simmer.

Add cutlets to sauce and simmer for 3 minutes, flipping halfway through simmering. Transfer cutlets to platter. Off heat, whisk in butter. Stir in parsley and cremini mushroom mixture. Season with salt and pepper to taste. Spoon sauce over chicken and serve.