Preheat the oven to 425 degrees F (220 degrees C).
Remove the woody ends of the asparagus by bending them at the end and snapping where it clicks naturally. Feel free to boil your asparagus for a minute or so if they are not as tender as they should be.
Grab 6 spears of asparagus, sandwich one of the rosemary sprigs and one of the anchovy fillets among the spears, and wrap a slice of pancetta around the middle to hold everything in place. Make three more bundles in the same way , and out them into a small roasting tray or pan with ? lemon. Drizzle with a little olive oil and roast in the pre-heated oven for 4 to 5 minutes, until the pancetta is crispy.
Remove from the oven, add your knob butter, and squeeze over the juice of your roasted lemon. Season of needs be. This will make a fantastic smoky sauce with your melted anchovies.
Recipe courtesy of Jamie Oliver