Cardamom Crusted Pork with Mushroom Sauce

Name: Cardamom-Crusted Pork with Mushroom Sauce
Ingredients: 1 1/2 cups chopped onion; 5 tablespoons olive oil; 2 1/4 teaspoons ground cardamom; 1 large garlic clove; 1 4-pound boneless pork rib roast; 1 1/2 pounds mushrooms, halved; 2 cups canned low-salt chicken broth; 1/2 cup whipping cream; 1 tablespoon all purpose flour; 1 tablespoon butter, room temperature