To serve, spoon over meat.
Keep leftovers in the fridge for up to a week, but allow to come up to room temperature before serving.
If you want to make it spicier, you can increase the red pepper flakes used, but I have found that they quickly become overpowering. I subtle hint of spiciness seems to provide the best balance.
If you are cooking a cut of beef suited for marinading, such as a flank steak, you can use the chimichurri as a marinade, but make sure to reserve some for serving. The brightness and crisp flavor is lost during the cooking process.