Sweet Corn Chowder

Name: Sweet Corn Chowder
Ingredients: 2 teaspoons olive oil; 1 medium onion, chopped fine; 2 cups cooked corn kernels (from 2 large ears); 2 medium Yukon gold potatoes, diced 3/8 inch thick; 6 fresh sage leaves, chopped; Generous pinch of chile pepper flakes, plus more for garnishing; 1/2 teaspoon sea salt, plus more as needed; 3 cups vegetable stock or Corn Broth, recipe follows; 5 cooked ears of corn; 1 teaspoon kosher salt; 10 whole peppercorns, black or white; 2 cloves garlic, smashed; 1 dried bay leaf; 1 medium onion, peeled and cut in half