Tuscan Porterhouse Steak with Red Wine-Peppercorn Jus

INGREDIENTS

• 3 tablespoons unsalted butter, cut into tablespoon pieces, divided
• 2 teaspoons black peppercorns, coarsely crushed (see Cooks' Notes)
• 5 sprigs fresh thyme
• 2 (4-inch) sprigs fresh rosemary
• 1 cup low-sodium chicken broth
• 2 teaspoons kosher salt
• 3 garlic cloves, crushed
• 1 (1 1/2-pound) porterhouse steak (1- to 1 1/4-inches thick)
• 1/2 cup medium-bodied dry red wine (such as Chianti, Rioja, or merlot)
• 1 tablespoon vegetable oil