First: I did not know National Chocolate Day existed. I need to celebrate it extensively.
Second: 'chocolately novel' can probably mean a lot of different things. My first though was something cozy and comforting and immediately Carola Dunn's Lady Daisy series came to mind. It's my favourite cozy-series. It's cute, has lovely characters and the author mostly manages to avoid all the things that usually annoy me in many other cozy-series (Ooops! I fell over another body! How did that happen? and conveniently stupid policemen)