Make the pickled cucumbers: In a large bowl, mix the cucumbers with the scallions. Add the vinegar and water, making sure the cucumbers are submerged in the liquid. Stir in the herbs, then set aside.

Make the lettuce wraps: In a large sauté pan, heat the oil over medium heat. Add the onion, garlic, scallions and mushrooms. Cook until the onion and mushrooms are soft, 4 to 5 minutes. Add the chicken or turkey and sauté until fully cooked through, 4 to 5 minutes more.

Stir in the Sriracha, soy sauce and rice-wine vinegar. Bring the mixture to a simmer and cook until the liquid has been mostly absorbed, 1 to 2 minutes. Remove from the heat and transfer to a serving bowl.

To serve: Place the lettuce leaves on a platter and top each with a scoop of room-temperature or chilled meat mixture. Top with pickled cucumbers and Fresno chiles, if using. Serve immediately.