In a large bowl, beat the softened cream cheese and sour cream together with a rubber spatula until completely smooth and no lumps remain. This takes about 2 minutes of vigorous mixing - do not rush it or you'll have streaks in your pinwheels.

Add the taco seasoning and stir until evenly distributed. Fold in the shredded cheddar, chicken, green chiles, cilantro, and scallions until everything is well coated and incorporated. The mixture should be thick and spreadable, not runny.

Lay one tortilla on a clean work surface. Spread one-quarter of the filling evenly across the entire surface, reaching all the way to the edges. Use an offset spatula or the back of a spoon for the smoothest layer.

Starting from the edge closest to you, roll the tortilla away from you into a tight cylinder. Apply gentle, even pressure as you roll to eliminate air pockets. Wrap the roll tightly in plastic wrap, twisting the ends to seal.

Place the wrapped rolls on a plate and refrigerate for at least 1 hour, preferably 2. This firms up the filling so you can slice clean, perfect rounds. The rolls can be refrigerated up to 24 hours at this stage.

Unwrap one roll and place seam-side down on a cutting board. Using a sharp chef's knife, slice into 8 even pieces, wiping the blade clean between cuts for neat edges. Arrange on a platter and repeat with remaining rolls. Serve chilled or at cool room temperature.