1 (15 ounce) can enchilada sauce (1½ cups), divided
3 medium zucchini (about 1 pound), trimmed
⅓ cup sour cream
3 tablespoons reduced-fat milk
1 cup shredded romaine lettuce
½ cup chopped fresh cilantro
1Preheat oven to 425°F. Heat oil in a large skillet over medium-high heat. Add onion, poblano and salt. Cook, stirring frequently, until the vegetables have softened and are beginning to brown, about 6 minutes. Reduce heat to medium if vegetables start to burn. Transfer to a large bowl. Add chicken, ½ cup cheese and ½ cup enchilada sauce. Stir to combine; set aside.
2Using a vegetable peeler or mandolin slicer, slice zucchini lengthwise into thin strips (see Tip). Discard any uneven and broken pieces. You should end up with 48 slices.
3Spread ¼ cup enchilada sauce on the bottom of a 9-by-13-inch baking dish. Lay three strips of zucchini on a clean work surface, overlapping the edges by ¼ inch or so. Place 2 generous tablespoons of the chicken filling across the middle of the zucchini strips. Gently roll the zucchini strips around the filling and place seam-side down in the prepared dish. Repeat with the remaining zucchini strips and filling. (You should have 16 enchiladas.) Top the zucchini rolls with the remaining ¾ cup enchilada sauce and ½ cup cheese.
4Bake until the sauce is bubbling and the cheese is melted, 20 to 25 minutes.
5Meanwhile, whisk sour cream and milk together in a small bowl. When the enchiladas have finished baking, top with lettuce and cilantro. Drizzle the sour cream mixture over the top.
To make ahead: Assemble enchiladas through Step 3. Refrigerate for up to 1 day.
Tip: The strips should be able to roll around the filling without breaking. Test a few strips to make sure you have the right thickness. If they break, slice them thinner.