In a large bowl, toss the endives with 1 tablespoon of the dressing and season with salt and pepper. Arrange the endives around the edge of a large platter. Add the avocados and the remaining dressing to the large bowl and toss gently with a rubber spatula. Arrange the avocados in the center of the platter. Scatter the scallion slices and pumpkin seeds over the salad and serve.