I just finished making cookies. The dough was enough to make multiple batches. I only have one baking sheet. Every time a batch was ready, I used new parchment paper on the baking sheet. Is this necessary or could I just re-use the same piece of paper till all my cookies are baked?
You can reuse parchment paper several times for your cookies (it also works for other dry dishes), depending on cooking time and temperature, with no problem. Change the paper when it gets dirty, dark and/or brittle as it may crumble beyond this point. I always do so with no difference in the results, saving both on money and waste.