Let's say your main keyword is white chocolate fudge.  If you write 300 word article with 'white chocolate fudge' too many times, you're guilty of keyword stuffing and your article may be unreadable.

However, if you take some of your related terms from google keywords, you're not stuffing but you get the results.

white chocolate fudge 6 times in your article gets you a keyword density of 2%.

you can increase the punch of that 2% by having

white chocolate cupcakes, best white chocolate, sugar free white chocolate, and white chocolate truffles.

You can easily make it readable as a list or a comparison. 

These receipes work equally well with white chocolate cupcakes and white chocolate truffles.  I've tried sugar free white chocolate and I can tell you you still get the best white chocolate fudge or truffles.

I think Google is now convinced that I'm talking about white chocolate, white chocolate fudge,don't you?