Do You Wanna Build A Snowman? (слэш)

Original this was for the 2016 Dean/Cas Secret Santa Exchange but the person who I was assigned to dropped out and everyone knows stuff happens but here it is. Loosely based on the prompt: After a blizzard shuts down the town and leaves them stranded at the Bunker, Dean takes the opportunity to teach Castiel how to build a snowman. (And then warms him up with a cup of hot chocolate...)