Heat oven to 425°.
Slice ends off sprouts and cut into halves.
Toss sprouts and odd leaves in 2 tbsp oil, 1 tsp salt and 1 tsp pepper.
Spread onto a baking sheet in a single layer and roast until leaves are browned and hearts are tender, 15 to 20 minutes.
Season with salt and pepper.
In a food processor, process remaining ½ cup oil, parsley, hazelnuts, cilantro, vinegar, garlic, remaining 1 tsp salt and 1 tsp pepper until smooth.
Toss sprouts in sauce until well coated.
Pour sprouts onto a serving dish.
Garnish with fresh parsley or basil if desired.
