Skillet Potatoes with Chard

Name: Skillet Potatoes with Chard
Ingredients: 2.5 pounds Yukon Gold potatoes (about 6 large), peeled and sliced into ¼” thick rounds; kosher salt, to taste; olive oil; 2 ounces pancetta, finely diced; 1 cup thinly sliced shallots, from about 1 or 2 large shallots; 1 tablespoon fresh thyme leaves, finely chopped; large pinch of red pepper flakes; 4 large garlic cloves, thinly sliced; 2 large bunches of Swiss chard (about 1 pound); finely grated lemon zest, from one small lemon; 1/2 cup heavy cream (or a few tablespoons more, as needed); 1 cup shredded aged cheddar (I used Cabot Clothbound) or gruyère; 1/2 cup panko bread crumbs