Why is it an interesting pairing? Both chocolate and wine go through fermentation, and each have different levels of tannins.

Darker the chocolate the bolder the tannins. Try to compliment tannin structure between the chocolate and wine. Big tannic Petite Sirah with a dark chocolate.
Consider the intensity of both the chocolate and wine. Lighter milk chocolate pairs with lighter red wines like a Grenache or Pinot Noir. A bittersweet chocolate pairs well with a more tannic wine like a Cabernet Sauvignon or Petite Sirah.
The chocolate’s creaminess should be considered when thinking about the wine pairing. White chocolate is a bit more creamy or buttery than darker chocolates try Viognier.
Let the chocolate melt and coat your mouth to truly taste the nuances. Then add the wine to taste both.
Lastly, like other wine and food pairings, experiment. Host a wine and chocolate party and rate different pairings.

Check out this short video about Wine + Chocolate Pairings.