Place potatoes into a wide-bottomed pot and add enough chicken stock to cover them halfway. Add the onion, rosemary, EVOO, some salt and pepper to the pot and place over medium-high heat. Cover the pot and bring up to a bubble. Simmer 10 minutes then remove the lid and continue cooking so the pan juices evaporate away.
When the liquid is nearly gone, shake the pan to coat the potatoes in the residual EVOO and smash them down lightly with a potato masher (you just want to burst and flatten them a little, don’t completely mash them).
Let the potatoes continue to cook and crisp until golden brown, 3-4 minutes. Serve with Florentine Dream Burgers.