A valance kit and mounting assembly secure a valance adjacent a window frame. A mounting block is securable in a clamp ring cavity of the window frame and includes a snap connector on the frame side thereof and a valance groove in each of the top and bottom sides thereof. The valance grooves extend in a width direction across the mounting block and have a depth dimension parallel with a plane of the window opening. A valance assembly includes a plurality of shrouds that together define the valance. Each of the shrouds is provided with a pair of snap ridges disposed facing each other and spaced substantially corresponding to a space between the top and bottom sides of the mounting block. The snap ridges are sized and positioned to engage the valance grooves in a snap fit. The universal mounting block is suitable for mounting various types of window treatments.