Beat egg whites (at room temperature) in a large mixing bowl until soft peaks form. Gradually add sugar, 1 tablespoon at a time, beating until stiff peaks form and sugar dissolves. Add baking powder and vanilla, mixing well. Fold in crackers and 3/4 cup chopped pecans. Pour mixture into a well-greased 9-inch pie pan. Bake at 325° for 1 hour.
Remove from oven, and invert pan onto a serving platter. Cool 40 minutes; remove pan. Top with whipped cream and toasted pecans. Cut into wedges to serve.