My sister, who bakes for a living out of her house, watched me pull butter straight from the fridge and cream it with sugar while it was still cold and hard, resistant against the mixer. "How long did that sit out?" "It didn't. I just took it out." She stopped what she was doing entirely. "That's the whole thing, right there." "It's just butter. I figured room temperature was more of a suggestion." "Room temperature butter traps air when you cream it. That trapped air is what holds the dough's structure while it bakes, before the butter fully melts. Cold butter doesn't trap nearly as much — it just melts fast and flat the second it hits heat, with nothing holding the dough up while that happens." She had me start over, butter properly softened this time, forty-five minutes on the counter instead of straight from the fridge. Same recipe, same oven, same tray. The cookies came out of the oven noticeably domed, soft in the center, nothing like the thin discs I'd been pulling out for months. I'd blamed my oven temperature, my baking soda's freshness, the altitude of my apartment, everything except the twenty minutes of patience I kept skipping every single time I decided I didn't feel like waiting for butter to soften.