How can you avoid those famous lumps?
Here's a list of possible actions:
1) If you're incorporating a powdery ingredient (flour, almond powder, etc.), you need to sift the powder in question before incorporating it.
Don't hesitate to sift together several or all the powders in a recipe, for example for a cake: flour + sugar + yeast.
2) For mixing, use a whisk instead of a maryse, spoon or spatula, as it mixes much better.
3) If, despite this, you're still faced with lumps, as a last resort, the mixer is your friend: giving your dough in preparation a good blow will liquefy it in a matter of seconds.
But don't use it on dough containing whipped cream or egg whites, as you'll destroy the airiness of the mixture.
What if it's not a powder you're mixing in?
You can use the same lifesaving gestures, but your problem probably stems from too great a temperature difference between the dough you're mixing in and the butter, and the latter congeals and clumps together.
The trick is to keep mixing, placing your dough in a bain-marie that's not too hot, or if possible, putting it in the microwave for 20-30 seconds.
To sum up: to avoid lumps with powders: sift, whisk, mix, and with fats: the same, but pay attention to temperature differences.
