Can you temper store-bought chocolate?
Yes, you absolutely can (Lindt dark chocolate bars work just fine).

Whether you can temper chocolate is simply a matter of whether there's enough cocoa butter (the fat that is actually crystallizing during the tempering process). You will want to have at least ~30% cocoa butter by mass if you want to temper the chocolate, but even 20% will work.

When you see a chocolate bar that says something like, "70% cocoa," that is the sum of the fat (cocoa butter) and non-fat parts (cocoa solids) of the cacao bean. That 70% might be divided between 30% fat and 40% cacao, for example, which is definitely sufficient for tempering.

If you want to know if a particular bar can be used for tempering, here's a quick test:


Read the label, and see if the primary fat is real cocoa butter
Make sure that the bar is at least 30% fat by mass


Small warning: different chocolates have different tempering curves. This is why dark, milk, and white chocolates generally have slightly different tempering curves. If you have a good, instant-read thermometer, it will help in the process of learning how to temper your chocolate of choice.