Fresh picked berries are at their peak of sweetness compared to the more tart berries found in the grocery store, so less sugar is needed. Make sure your pie is really bubbling before you pull it from the oven to insure all the juices gel and don’t leave a soupy mess when the pie is cut. If the crust edge is browning too much then cover it with a pie shield or foil.
Heat oven to 400F. Line 9-inch pie plate with dough. Trim and flute edge. (Roll out dough scraps and cut shapes for decoration. Sprinkle shapes with sugar, if desired.)
Sprinkle cookie crumbs over bottom of pie shell and chill while preparing topping and filling.
For topping: combine all ingredients in a bowl working the butter into the dry ingredients until clumps form. Chill it.
For Filling: Place berries and rhubarb in a large bowl. Drizzle with heavy cream, lemon juice and vanilla; gently toss to coat. Add sugar and flour; toss again.
Spoon into pie shell. Sprinkle crisp mixture over the top.
Bake for 60 to 70 minutes or until pie is bubbling and crust and topping are golden brown.
Let cool to room temperature or serve just slightly warm.