Clams with Chorizo, Leeks, Tomato, and White Wine

2 tablespoons olive oil 6 ounces best-quality fresh chorizo, thinly sliced 1 or 2 medium leeks (white parts only), trimmed and sliced (about 2 1/2 cups) 4 garlic cloves, peeled and finely chopped, plus 2 garlic cloves, peeled and cut in half Salt and freshly ground black pepper to taste 1 cup dry white wine…