Strawberry-Rhubarb Pie with Sour Cream Crust

INGREDIENTS

2 1/2 cups

all-purpose flour

2 tbsp

granulated sugar

1/2 tsp

fine salt

1/2 cup

shortening, frozen and cut into small pieces

10 tbsp

cold unsalted butter (1 1/4 sticks), cut into small pieces

1/2 cup

plus 2 tablespoons sour cream

All-purpose flour, for dusting the work surface

1 1/4 cups

granulated sugar

1/2 cup

cornstarch

2 lb

rhubarb, ends trimmed and cut into 1/2-inch pieces (about 7 cups)

1 lb

strawberries, washed, hulled, and cut into 1/2-inch pieces (about 3 cups)

2 tsp

freshly squeezed lemon juice

large egg white, beaten