Toss pulled pork with BBQ sauce. Add to onion for last couple minutes of cooking to heat through.
Meanwhile, grate cheese and butter bread slices on one side.
Top 3 or 4 slices of bread evenly (on unbuttered side) with pulled pork and cheddar cheese. Top with remaining bread and cook in same pan you used to cook onions, over medium-high heat, until golden brown on each side (3-4 minutes per side).
Serve warm.
Notes
These are also good with bacon bits added, or roasted peppers.
Recipe by Hidden Ponies at https://hiddenponies.com/2013/01/grilled-pulled-pork-sandwiches/