I have a bit of a thing for dark chocolate, and of all the supermarket brands, nowhere does it better than Sainsbury's Taste the Difference Belgian Dark Chocolate (£2.30).
Sainsbury's remind me of my childhood, so you might say I'm biased, but the proof is in the pudding, or the bar, for this matter.
The 72% Dark Chocolate bar is sold in the baking area of the store, but I see it as something to nibble on when you want something sweet, but not too sugary.
Unlike a lot of dark chocolates ranges on the market, this bar is remarkably smooth, and not as bitter as you might expect. I've found bitterness is something producers struggle with - cacao is naturally a neutral flavour, which has no sweetness to it at all, which is probably why people consider it bitter; cacao is not naturally bitter, but in comparison to the Western understanding of what is chocolate, dark chocolate can seem bitter.
Either way, I don't just use this chocolate as a sweet-fix when I'm in the mood for dessert, I use it in chilli and beef stews - it works wonderfully, and the naturally occurring sugars in the bar make stews and chillies all the more delicious. Although many would consider 70% dark chocolate a high percentage of cocoa mass, it's not that high, and it works better than some 85% chocolates I've previously tried.
If you're not as daring as myself then the chocolate is delicious eaten alone.