Cook the pasta: Bring a large pot of salted water to a boil. Cook pasta until just al dente (usually 1 minute less than the package suggests). Drain and rinse under cold water to stop cooking. Shake off excess water well.

Crisp the bacon: While pasta cooks, fry bacon until crisp. Drain on paper towels and crumble. Reserve a tablespoon of bacon fat if you want a deeper flavor in the dressing.

Make the dressing: In a large bowl, whisk together mayonnaise, Greek yogurt, ranch seasoning, garlic powder, onion powder, and black pepper. Add 2 tablespoons buttermilk to start. Whisk until smooth. If you like, whisk in the reserved bacon fat for extra richness. Adjust thickness with more buttermilk until creamy and pourable but not runny.

Season the base: Taste the dressing. Add a pinch of salt if needed. Keep in mind the bacon and cheese will add saltiness later.

Add the mix-ins: Fold in cooled pasta, chicken, cheddar, green onions, and celery. Toss gently until everything is well coated. If adding tomatoes, jalapeño, peas, or pickles, mix them in now.

Chill to marry flavors: Cover and refrigerate at least 30 minutes, up to 24 hours. The pasta will absorb some dressing as it sits.

Finish and serve: Right before serving, stir the salad and check the texture. If it seems dry, splash in a little milk or buttermilk and add a spoon of mayo or yogurt. Fold in the crumbled bacon to keep it crisp. Taste and adjust salt and pepper.

Garnish: Top with extra cheddar, green onions, and a grind of pepper. Serve cold.