Preheat an outdoor grill to medium high heat and lightly oil grate.
In a food processor, chop 3 cloves of garlic until minced. Add the basil and pine nuts and pulse to mix together.
With the food processor running, slowly pour in the olive oil, stopping a few times to scrape down the sides.
Add the next 3 ingredients (Parmesan cheese through red pepper flakes) and pulse until blended.
Season with salt and pepper to taste.
Rub the steaks with 2 clove minced garlic and season to taste with salt and pepper.
Place steaks on grill, turn heat down to medium, and grill to desired doneness, 3 to 4 minutes per side for medium.
Baste the steaks occasionally with some of the pesto. Serve hot off the grill, and top with any left-over pesto sauce.