Spicy Shepherds Pie with Chorizo

Name: Spicy Shepherd's Pie with Chorizo
Ingredients: 2 pounds russet potatoes, peeled and quartered; Kosher salt; 1 tablespoon extra-virgin olive oil; 8 ounces fresh chorizo, casings removed; 12 ounces ground beef; 1 bunch scallions (white and light green parts only), chopped; 2 cups frozen corn (preferably fire-roasted); 1 poblano chile pepper, chopped; 2 tablespoons tomato paste; 1/2 teaspoon ground cumin; 1/2 teaspoon chili powder; Freshly ground pepper; 1 14.5-ounce can diced tomatoes with green chiles; 1 cup low-sodium chicken broth; 1/2 cup sour cream; 3 tablespoons unsalted butter; 1 1/2 cups shredded pepper jack cheese (about 6 ounces)