For crust: combine flour, sugar, and salt in a large bowl. Add butter and toss with four to coat. Use your fingers to squish each cube of butter flat, then toss it all again with your hands—that’s all it takes, no need to work it in more. Gradually splash in cold water, using a fork to combine, until dough comes together in a shaggy ball. When you press the dough with your fingers it should hold together, but just barely—you might not need all the water.

Turn your dough onto a floured countertop and roll it out into a big rectangle, no need to be exact. The lumps of butter in the dough should be just pliable enough that they smear flat as you roll.  Fold the short sides of the rectangle towards the center to meet each other, then fold the whole thing in half like a book. Cut the folded dough in half, then wrap one of the halves in plastic wrap and stick it in the fridge. Roll out the remaining half to fit your pie pan, then line your pan. Trim excess to hang approx. 1″ over the edge of your pie pan, then put the whole pan in the fridge to chill.

While dough chills, combine all filling ingredients in a large bowl. Rhubarb should look sandy.

Remove pan from fridge and pour filling into bottom crust. Roll out the other half of the dough to create the top of the pie—I particularly like a lattice top for rhubarb pie, since it allows excess moisture to escape. After covering filling and crimping edges, stick the pie in the fridge and preheat the oven to 425 degrees.

When pie is chilled and slightly firm, approx. 30 minutes, wash the top crust with the beaten egg and sprinkle with sugar. Bake at 425 degrees for 15 minutes, then reduce heat to 350 and bake for 45 minutes more. Bake it ’til it’s deeply golden and the filling is bubbling—it’s hard to overbake a pie. Allow pie to cool completely before cutting so tapioca starch can set. Eat with vanilla ice cream for dessert, or (my favorite) with yogurt for breakfast.