Wash and dry all produce. Adjust rack to upper position and preheat oven to 450 degrees. Set aside sour cream at room temperature. Cut potatoes into 1/2-inch-thick wedges. Trim, then thinly slice scallions, separating greens and whites. Slice pickles and tomatoes into thin rounds. Mince chili, removing ribs and seeds first for less heat.

Toss potatoes on a baking sheet with a large drizzle of oil. Season with salt, pepper, and 1 TBSP barbecue seasoning (1 packet). Roast in oven until tender and crisped, 20-25 minutes, flipping halfway through.

In a large bowl, combine turkey with remaining barbecue seasoning and 2 tsp ketchup (save the rest for spreading on buns). Season turkey mixture with salt and pepper (we used 11/2 tsp kosher salt). Shape into four 3/4-inch-thick patties.

Heat a large drizzle of oil in a large pan over medium-high heat (use a nonstick pan if you have one). Add patties and cook until no longer pink in center, 4-6 minutes per side. (TIP: Lower heat to medium and cover pan if if patties are browned before meat cooks through.) Meanwhile, split buns in half and toast in oven or toaster until light golden, 2-3 minutes. Transfer patties to a plate to rest once done. Wipe out pan.

Melt 2 TBSP butter in pan used for patties over medium-high heat. Add scallion whites and cook, tossing, until just softened, 1-2 minutes. Pour in 1/4 cup water and bring to a simmer. Remove pan from heat and whisk in cheddar and sour cream until smooth and wellcombined. Season with salt and pepper. TIP: If queso thickens before serving, warm over low heat, stirring constantly.

Spread bun bottoms with rest of the ketchup, then place patties on each and spoon a little queso over. Top with pickle, tomato slices, and remaining bun halves. Divide between plates with potatoes to the side. Drizzle remaining queso over potatoes. Garnish with scallion greens and chili (to taste).