melt in mouth
melt in (one's)/the mouth
Of food, to be soft or tender, and, typically, delicious. The phrase is often quite literal. This decadent chocolate cake positively melts in the mouth. I've never had such a perfect steak in my life! I swear, it melted in my mouth.
melt in one's mouth
1. to taste very good. (Also can be literal.) This cake is so good it'll melt in your mouth. John said that the food didn't exactly melt in his mouth.
2. [of meat] to be very, very tender. My steak is so tender it could melt in my mouth. This filet will melt in your mouth!