Corn Coconut Soup

Name: Corn Coconut Soup
Cook time: 2 h
Total time: 2 h
Cuisine: Asian, Thai
Ingredients: 2 large yellow onions; 3 quarts (2.8 liters) water; 4 large ears or 5 medium-large fresh corn, kernels cut from cobs, cobs reserved; 1 (1-inch) piece ginger, peeled and thinly sliced; 4 garlic cloves, sliced; 2 tablespoons (30 ml) canola, safflower, or another neutral oil; 2 1/2 teaspoons kosher salt, plus more to taste; 1 (13.5-ounce or 400-ml) can full-fat coconut milk, well-stirred; Juice of half a lime; To garnish: Fresh cilantro leaves, lime wedges, toasted coconut flakes, (see below for next three) chile oil, pickled shallots, and/or crispy shallots