I made this recipe last weekend and while it came out very tasty, there was the occasional gritty texture/crunch similar to sand at the beach getting in your mouth. This was more of an issue since the recipe produces a more cake-like cookie, so the grit stands out more.
The batter was pretty thick and difficult to stir, but it seemed fairly well mixed.
I have a feeling this is somehow related to the baking powder/soda, but not entirely sure.
[EDIT]
SAJ14SAJ mentioned the creaming method being a possible source to the issue. I wasn't entirely sure with that step, how exactly would you "cream together" sugar and butter? It said only to soften and not melt, and it definitely didn't appear "creamy" when I was done with it.
Best Answer
It is unlikely that the chemical leavening was a contributor to perceived grittiness. If you had extra leavening, especially in clumps large enough to perceive, you would also have a very metallic off taste, that surely would have been worth mentioning.
These cookies are made by the creaming method, and have very little water. The most likely suspect to cause graininess is the sugar.
If there were clumps in the granulated sugar for any reason, they might not dissolve completely during the mixing or baking, leaving a gritty texture.
The way to prevent this, if you consider the effort worth it, is to sift the sugar through a very fine strainer prior to using it in your dough.