Regulus was going to protest Duncan taking the bread, but he had a spoon in his mouth, and any objection died as he swallowed jam.
He stood up, taking the jam with him, and followed Duncan as the man started... doing things. Regulus understood the tea kettle when it was found and filled with water. He'd missed the tea kettle his first perusal through the kitchen. But... aside from that, he had no idea what Duncan was doing. Every other item or object the man touched was an amalgamation of 'muggle,' the delineation of which Regulus simply did not know how to discern.
"Uh..." he had to stop and think. "Darjeeling tea."