When chicken and potatoes have 5 minutes left, pierce green bean bag with a fork; place bag on a plate. Microwave until tender, 1-2 minutes. (TIP: No microwave? No problem! Steam beans in a small pot with a splash of water until just tender, 5-7 minutes.) Transfer to a medium bowl and toss with 1 TBSP butter, salt, and pepper. In a second small bowl, combine remaining mayonnaise and sriracha to taste.