Why does one brand of chocolate bar feel so velvety smooth in your mouth but the next one feel so rough?

Let’s get down to the nitty gritty, shall we? (pun intended!)  It all depends on particle size, or the fineness of grind. 

When cocoa beans are shelled and roasted, the nibs are ground up and heated to form fluid chocolate called chocolate liquor, cocoa mass, or unsweetened chocolate.  When chocolate liquor is then blended with other ingredients like sugar and milk powder, the resulting paste is ground up even further.  This process is called “refining.” 
Read more