A couple of years ago I made farmer cheese from this recipe. It turned out great: creamy and delicious. Today I made the same recipe, and it turned out dry and crumbly instead. What would explain the inconsistency? The only thing I did differently is halve the recipe this time, but I can't see why that would alter the texture of the finished product.
Based on lots of experience making farmer's cheese (and backed up by the book One Hour Cheese), there are three factors which control the scale of creamy to dry & crumbly:
- the degree of acidity at which you set the curd;
- the length of time you cook it (keep it at 180F+)
- the length of time you drain it
So my guess would be that you increased two out of three of the above, or all three, without intending to. For example, you might have added the whole amount of vinegar instead of halving it, or, because you were draining half as much, it could have dried faster. Note that all textures from gloopy to sawdust are "legitimate" farmer's cheeses, and in Russian delis you can buy cheeses with the whole range of textures, for different applications.
Also, your cheese is not unsalvageable. Depending on what you're using it for, you can add a little cream, sour cream, or full-fat yogurt to make it creamier. And for that matter, dry and crumbly is perfect for making blintzes.
Most likely a critical mass is required. I would recommend the full recipe.