Combine the four, walnuts,and sugar. Mix together ,then add the butter and the egg yolk. Mix with electric mix until crumbly. Press about 1 1/2 cups of the mixture in an ever layer into the bottom of a 9 1/2 inch spring form pan. Arrange the peaches in the pan.Working from outside in make sure you have cover the bottom layer of the crumble you have pressed down.
Sprinkle the rest of the crumble mixture evenly over the peaches. Bake for 50 minutes or until its lightly brown and the peaches are bubbling thought the crumble or if you like it crispy crust until it's med dark on edges. Remove from oven let cool 15 minutes. Remove from pan and serve warm or cold with a big scope of Whipped Cream.