Preheat the oven to 350 degrees F (175 degrees C). Spray a 9x13-inch baking dish with cooking spray.

Place broccoli into a microwave-safe dish with 2 tablespoons water. Cover and microwave on high until broccoli is steaming and bright green, 2 to 3 minutes.

Meanwhile, whisk condensed soup, mayonnaise, lemon juice, curry powder, salt, and pepper together in a bowl until well combined.

Transfer broccoli to the bottom of the prepared baking dish. Layer cooked chicken over broccoli, then pour soup mixture over top. Sprinkle Cheddar cheese over the casserole, followed by crushed cornflakes and almonds.

Bake, uncovered, in the preheated oven until casserole is bubbling, cheese is melted, and topping is browned, about 30 minutes.