Heat oil in non-stick wok over medium heat. Add the pancetta and cook, stirring occasionally, until crisp, about 5 minutes. 

Transfer the pancetta to a paper-towel-lined plate. 

Add the garlic to the skillet and cook for approx 30 seconds. 

Add chilli flakes, Brussels sprouts, and 1/2 tsp. salt. 

Cook until the sprouts are crisp-tender, 2 to 3 minutes. 

Stir in half of the cheese and the lemon juice and remove from the heat.

Boil the pasta according to package directions until al dente. 

Drain the pasta, and then add it to the skillet along with 1/4 cup water

Cook over medium-high heat, tossing and adding more water as needed, until the Brussels sprouts are tender, about 1 minute. 

Stir in the pancetta and season generously with black pepper. 

Taste and season with additional salt and lemon juice, if required

Serve topped with the hazelnuts and the remaining cheese.