Preheat oven to 450°F

Put Brussels sprouts in large mixing bowl. Add olive oil, pancetta and season with 1/4 tsp of salt and a pinch of pepper. Mix until oil coats the sprouts.

Put a large oven proof skillet over medium high heat and dump the sprout mixture into hot skillet. Cook stirring often, until pancetta renders its fat and the sprouts start to brown (4 mins).

Transfer skillet to oven to roast the sprouts and periodically stirring with a large spoon or shaking the pan to move the pancetta from burning. 15 mins.

For lemon aioli sauce-combine mayonnaise, lemon juice, zest, garlic, salt and pepper. Mix well and refrigerate in tight covered container. Can make up to 3 days ahead.