For the longest time, I thought lamb was strictly reserved for holidays like Christmas and Easter. (My mom doesn’t eat lamb, so I only ever ate it when I celebrated holidays at friends’ houses). But about five years ago, I had my first lamb burger at a restaurant in Brooklyn, and I realized what I’d been missing. It was one of the best burgers I’d ever had, and I became determined to create my own version—in slider form, that is. The best thing about the burger was how well-seasoned it was. When cooking lamb, you don’t want to drown out its unique flavor, but you do need enough of a kick to counterbalance it. That’s where harissa—a Tunisian chile paste made up of peppers, citrus, cumin, coriander, and caraway seeds—comes into play. Its flavor perfectly tempers the richness of the lamb, and trust me: Once the sauce (or powder; it’s …