Shave off ends of sprouts and remove outer couple of leaves. Then with a chef's knife, shred like you would cabbage. Cover and place in fridge until you are ready to cook.
Melt butter in a saute pan and add the brussel sprouts with a finely chopped serrano chili. Saute gently without too much browning until sprouts are limp and still "to the tooth" but done. Salt to taste and add pepper.