Prime Rib Roast with Cognac & Green Peppercorn Sauce

Ingredients

• 4 lb (2 kg) bone-in prime rib roast
• sea salt and freshly ground black pepper, to taste
• 1 bunch fresh sage
• olive oil, for roasting
• 6 to 8 large sprigs fresh rosemary
• 1 onion, unpeeled, quartered
• 2 heads garlic, halved crosswise
• 2 tbsp (30 ml) green peppercorns in brine, drained
• 3 tbsp (45 ml) salted butter
• FOR THE COGNAC AND GREEN PEPPERCORN SAUCE
• 4 tbsp (60 ml) salted butter
• 4 large garlic cloves, crushed
• 3 tbsp (45 ml) green peppercorns in brine, drained, finely chopped, divided
• ¾ cup (175 ml) cognac
• 1 cup (250 ml) crème fraîche or whipping cream
• 2 tbsp (30 ml) lemon juice
• 3 tbsp (45 ml) strong Dijon mustard