1 pound fresh rhubarb, chopped (can be hard to find)
1 egg yolk
2 T. white sugar
Preheat the oven to 400 degrees. In a large bowl, add 1 c. white sugar, the sliced strawberries and chopped rhubarb, and toss together. In another small bowl, combine the 1/4 c. water with 2 T. cornstarch and add this mixture to the strawberries/rhubarb bowl, toss to combine. Let stand for 30 minutes.
Pour filling into the prepared pie crust, and spread little bits of the butter around the top of the filling. Cover with the top crust and seal the edges, using water if necessary.
Use a pastry brush to apply yolk to the top of the pie. Sprinkle with the 2 T sugar and cut holes/lines in the top to let steam escape. Bake for about 1 hour. This is a little tricky because I'm pretty sure my oven is off from other people's "normal" ovens. When the top looks golden, you're golden. Let this pie stand on a cooling rack for at least 2 hours, or it will still be runny. MUST SERVE with vanilla ice cream.
I forgot to take a picture of the cross section of the pie, but here's the whole thing when I pulled it out of the oven.