Remove the large, dark green outer leaves of the romaine to expose the heart. Set the leaves aside for another use. Trim the edge of the root but keep it intact. Cut the lettuce hearts in half directly through the root so they stay intact. Set aside.
Dice the onion and mince the garlic. Chop the bacon into small cubes and set aside. Thaw the peas before cooking.
In a wide skillet, cook the bacon over medium heat until browned and crispy. Remove from the heat and use a spoon to remove most of the bacon fat. Add the onion and sauté for a few minutes until softened. Then, add the minced garlic and sauté for 30 seconds until fragrant.
Add the broth to the skillet and bring to a simmer. Season with a pinch of pepper.
Place the lettuce hearts into the skillet, cut side down. Let simmer for a few minutes then flip over. Simmer another minute or two until the lettuce is tender. Remove the lettuce from the skillet and set aside on a plate.
Add the peas and cook until the broth has reduced slightly, and the peas are cooked through. Check the seasoning, adding salt only if needed. Add the lettuce back to the pan to rewarm if necessary.
To serve, spoon the peas and bacon into a serving dish along with some of the braising liquid. Nestle the lettuce hearts on top of the peas and garnish with chopped parsley if desired. Enjoy!