Using the recipe of your choice (mine is the Best of Both Worlds Pie Crust on this site), prepare, roll and plate a 9 inch pie crust. This is a great step to do one or two days in advance. Keep covered in the refrigerator until ready to use.
I always make the pie crust and crumble topping at the same time when I’m using my food processor. After I make the crust and have the disc chilling in the refrigerator, I use the same food processor (I don’t even wash it – just leave the crust crumbs in there) and make the crumble topping.
Place the flour, oats, brown sugar, cinnamon and salt together and pulse to mix.
Cut 4 tablespoons of butter into small pieces and scatter over the dry mixture. Pulse to blend well, until all of the butter is cut in and the mixture looks like coarse meal.
Turn mixture out into a bowl and bring together with your hands, making small clumps of crumble. Keep in the refrigerator until ready to use, or if making in advance (another great step), store in an airtight bag or container in the freezer.
Preheat oven to 425
Peel and slice peaches into 1/4 inch slices and place into a large mixing bowl.
Slice plums into 1/4 inch slices (keeping skin on) and add to bowl.
Add lemon juice, 1/3 cup sugar and vanilla. Mix gently to distribute ingredients.
In a small bowl or ramekin, combine 1 tablespoon of sugar, 3 tablespoons of cornstarch and spices. Add to the fruit mixture and combine to coat evenly.
Turn filling into the chilled pie shell, leaving behind any extra juice in the bowl (I like to use a slotted spoon).
Top with crumble topping.
Place on bottom rack of oven and bake at 425 for 15 minutes.
Lower oven temperature to 350 and continue baking for another 30 minutes or until the juices bubble and the pie is golden brown.
Remove from oven and let cool for a minimum of four hours. It needs to completely cool so that the juices set. Enjoy!