I used indirect heat to grill the pork butt. Prepare the grill by heating the outside burners and rub the pork with your favorite rub or spices. Sear the pork on all sides over one of the heated burners. Once seared, place in the middle of the grill where it is not above direct heat. Flip occasionally and brush with your favorite bbq sauce every time you flip. This will take approximately 45 minutes to an hour.
While the pork is cooking bring a large pot of water to a boil and pour 2 tbsp of salt in the water. Pour all the shells into the water and cook until al dente. Dump into a colander and shake out the excess water.
Melt butter in the same pan you boiled the pasta with at a medium heat. Saute white onions and pour milk and cheese into the pot and stir. Lower heat and keep stirring until smooth and creamy. Add milk if it is too chunky or more cheese if runny. Dump pasta into the cheese and stir until shells are covered with cheese. Dump the cheesy shells into a 13×9 casserole pan.
Once the pork is done, let it rest for five minutes. Slice pork and the pull the slices using two forks. Toss the pork on top and sprinkle some cheese and green onions on top. For added flavor try sprinkling the rub on top of the dish or drizzle with bbq sauce. Place in oven for 20 minutes at 400 degrees.