Chef John's Hamburger Hash

Instructions

• Cut a 1/4-inch slice off the bottom each potato so it sits flat on a cutting board. Cut some more 1/4-inch slices straight down and then cut potatoes into sticks. Turn sticks and cut across to create a uniform dice. Transfer to a bowl of cold water.
• Combine butter and olive oil in a skillet over high heat until butter melts. Add ground beef and cook, breaking up with a flat-edge utensil, until crumbly, about 5 minutes.
• Drain potatoes and add to the beef with a nice pinch of salt. Reduce heat to medium-high and cook, stirring occasionally, until potatoes just start to soften, 5 to 7 minutes. Smooth mixture in the skillet and press against the bottom of the pan to help everything get nice and crusty.
• Stir in onions and mushrooms and add another pinch of salt. Cook, stirring occasionally, until onions and mushrooms have softened up and taken on some beautiful color, 5 to 7 minutes. Season with black pepper, cayenne, and rosemary.
• Add bell pepper, poblano pepper, and another pinch of salt. Cook until peppers are tender and the rest of the ingredients are dark and crispy, about 5 more minutes.
• Stir in green onions and cook for a few more minutes. Remove from the heat and serve.