Instant Pot Winter Chicken Panzanella Salad

sourdough bread, cut into 1-inch cubes

schmaltz (chicken fat), melted

Kosher salt and freshly ground black pepper

slices pancetta

boneless, skinless chicken breasts

unsalted butter

large bunches rainbow chard (about 2 pounds), leaves roughly chopped and stems chopped into 1/4-inch pieces

large leek, white and light green parts only, sliced thin into half moons

dry white wine

fresh thyme leaves 

Lemon wedges, for serving