Clam and Cod Chowder

Name: Clam and Cod Chowder
Ingredients: 2 tablespoons olive oil; 2 tablespoons unsalted butter; 1½ pounds small Yukon Gold potatoes, peeled, halved, quartered if large; 2 large leeks, white and pale-green parts only, finely chopped; 4 celery stalks, finely chopped; 4 sprigs thyme, plus leaves for serving; Kosher salt and freshly ground black pepper; ⅓ cup dry white wine; 4 cups fish stock or bottled clam juice; 2 cups heavy cream; 4 pounds littleneck clams, scrubbed; 2 pounds skinless cod or haddock, cut into large pieces; Hot sauce and lemon wedges (for serving)