The headline says it: The first and the second half of the series have a big variance between them.
The first half is cute, funny romance between a cold, clever, rich businessman (36 y.o) and vivid, somewhat silly, poor yet brilliant chef (21 y.o) which easily deserves at least 9/10 rating, if not higher. The focus is on the cooking aspect, the age and social gap between the main protagonists isn't really crucial, and everything is going in a smooth, fast pace (in fact sometimes too fast - I wouldn't mind having some subplots to get a bit more attention).
Then second half comes, and things change: focus shifts from cooking to business, social gap becomes more prominent, new (and often unnecessary) subplots and characters are introduced for the sake of conflict. Most importantly, and I'm not sure if it was the author's intention: the expected issues of age gap really start to show up. While ML is mature and acts maturely in the relationship, the FL is/does neither. In the end, it feels more like a father struggling to manage his teenage daughter, rather than a romance between two adults.
A pity. The first half was really promising, and if it was more expanded at the expense of the second half, it would make a great series overall. The way it is though, I cannot give it better rating than 7/10.