He doesn't bother to hide his smile. Dick's over the top reaction is classic and partially put on for Bruce's benefit, he's sure. It also means Dick is in a good mood, something that pleases him.

The second mug exchanges hands not without Bruce noticing the changes made to the first. "We should have brought a third bag. Two may not last the trip," he teases, also with a straight face. "Marshmallow addiction. Should I schedule some counseling?"