If Dream thinks his method of communication is going to startle Loki, it doesn’t. He’s aware of what Dream is and assumes he must have some abilities and as far as magic goes, that sort of communication should be easy for the likes of him.

Loki answers as if Dream were standing next to him, assuming he could hear him anyway. Typically, if you could project, the idea was that you could hear the message in return. And if not, it isn’t as if this is a life or death situation. “I am brewing a pot, there will be plenty if you would like to try some.”

He might be jealous and worried about how close Hob and Dream might be, but he also knows that Hob cares a lot about Dream and therefore Loki will do his best to be polite, even if only just.