Prepare the herbed yogurt: in a small bowl mix the 2 tbsp Greek yogurt with the 1 tbsp chopped dill and a pinch of salt and black pepper. Taste and adjust — the yogurt should be tangy and herbaceous. This chilled, creamy component will contrast the warm salad and mellow the beets' earthiness.

Warm and season the lentils: heat a small skillet over medium heat and add 1 tbsp extra-virgin olive oil. Once shimmering, add the minced shallot and cook 1–2 minutes until translucent — this softens the shallot and draws out sweetness. Add the minced garlic and cook 20–30 seconds until fragrant (don’t brown it; burnt garlic tastes bitter). Add the 3/4 cup cooked green lentils and a pinch of salt. Stir and cook 2–3 minutes until the lentils are just warmed through. Warming releases their starches and makes them more aromatic; it also helps them absorb the dressing.

Bloom the vinegar: turn the heat to low. Add the 1 tsp sherry (or red-wine) vinegar directly to the warm lentils and stir for 30 seconds to deglaze the pan and bloom the acid so it mellows and integrates with the oil and shallot. If the pan looks dry, add a teaspoon of water to loosen any stuck bits — this captures flavor.

Quick-poach the beet slices: while the lentils warm, bring a small pot of water to a gentle simmer (not a rolling boil). Add a small pinch of salt and a splash (about 1 tsp) of the same vinegar to the water. Submerge the sliced precooked beet for 30–60 seconds — just long enough to warm, slightly infuse with acid, and soften the edges. Because the beet is already cooked, this step is about temperature and flavor, not cooking through; over-poaching will make the slices mushy and leach color.

Toast the walnuts: while the beets and lentils finish, dry-toast the roughly chopped walnuts in a small pan over medium heat 1–2 minutes, shaking the pan often until they smell toasty and show tiny darker flecks. Toasting releases their oils and intensifies aroma; keep a close eye because nuts burn quickly. Remove from heat and set aside.

Assemble and dress: transfer the warm lentils to a shallow bowl. Arrange the warm beet slices on top. Scatter the toasted walnuts and 1 tbsp chopped parsley over the salad. Drizzle the olive oil left in the pan (if any) or the measured 1 tbsp over everything, then season with freshly ground black pepper and more kosher salt to taste. The warm lentils will take up the oil and vinegar, coating each bite and creating a silky mouthfeel that complements the cool yogurt.

Finish with the herbed yogurt: spoon the dill-yogurt in quenelles or small dollops over the salad, or serve alongside so diners can mix as they wish. The cold, tangy yogurt contrasts the warm ingredients and tames the beets' earthiness while adding creaminess and freshness.

Serve: serve immediately while lentils and beets are still slightly warm so you get the best temperature contrast. Leftovers can be served chilled the next day, but textures will be different (lentils absorb more dressing; walnuts soften).