This rhubarb berry slab pie is the perfect baked good for a large crowd or potluck as the pie can be easily cut into smaller pieces! (Jump directly to the recipe.)
This post was sponsored by California Grown. I was compensated for this post and for developing the recipe. However, all opinions below are completely my own.
I moved to California 20 years ago this coming May. Strangely I’ve never really thought about my life here in California, but I have slowly evolved into being a Californian. The things I mocked when I initially moved here (meditation, the obsession with locally grown seasonal produce, wearing a sweater if the temperature dips under 65°F) are all things I’ve come to embrace. Nothing more so than the seasonal and local food though. Honestly if there is ANYTHING that would peg me as an insufferable Californian, it would be the fact that I’m a spoiled brat when it comes to fruits and vegetables.
Nothing makes this more evident than when I get SUPER excited to see rhubarb at the grocery store and decide to share it on Instagram…only to have folks around the world proclaim how jealous they are. Apparently, rhubarb shows up early here in California because…well because we’re California. We grow one-third of the vegetables for the entire nation and two-thirds of the fruits! So, of course, it’s super easy for me to be THAT guy who buys local food and highlights it all the time.
I will admit though, I do go crazy when Spring arrives and I see rhubarb. I’ve been going rhubarb crazy lately and that means I’ve also been going a little bonkers with berries as well. Rhubarb and berries are a total winning combo. Recently AJ and I took a little mini-vacation jaunt up to Sonoma (if you follow me on Instagram you probably saw some IG stories of my time up there at my friend Peter and Grant’s place) and I brought along some rhubarb, strawberries and blueberries because, like usual, I had bought too many of them to eat before our trip. Luckily our hosts decided to throw an impromptu brunch (as one does, when you live in Sonoma) and it was a great excuse for me to bake up a Rhubarb Berry Slab Pie. Once you get your hands on some rhubarb, you’ll be wanting to bake this one up too!
Rhubarb Berry Slab Pie
- 2 cups all-purpose flour 280 g
- 1 cup white whole wheat flour 150 g
- 1 1/2 cups quick cook or baby rolled oats 150 g
- 1 teaspoon kosher salt
- 1 1/2 cups unsalted butter 340 g or 3 sticks
- 3/4 cup cold water plus an additional 1/4 cup if necessary
- 3 cups halved strawberries 455 g or 1 lb
- 2 cups blueberries 300 g or 10 1/2 oz
- 3/4 cup granulated sugar divided, 150 g
- 1/4 cup cornstarch 35 g
- Zest of 1 lemon
- 1/4 teaspoon kosher salt
- 1/4 teaspoon fresh ground pepper
- 5 cups 1/2-inch chopped rhubarb 625 g or 1 lb 6 oz
- 1 teaspoon balsamic vinegar
- 1 large egg
- 1 tablespoon cold water
- 2 tablespoon Turbinado sugar or white sugar
Make the crust.
Place the flours, oats, and salt in a large bowl. Stir with a whisk. Cut the butter into 1/2-inch chunks. Sprinkle over the dry ingredients and toss to coat. Using your fingers, press and smash the cubes into small bits, about the size of peas (but flat, not round). Sprinkle 3/4 cup of water into the bowl and stir with a fork until it starts to get shaggy. Sprinkle more water, a tablespoon at a time, if the dough looks too dry.
Once the dough starts to look shaggy, start to massage it with the palms of your hand to incorporate the dry ingredients. Divide in half, pat into a 1-inch thick disk. Cover with plastic wrap and chill in the refrigerator 1 hour or overnight.
Make the filling.
Once the dough is chilled, place the strawberries, blueberries, 1/2 cup sugar, cornstarch, lemon zest, salt and pepper in a large mixing bowl. Fold together and set aside.
Place rhubarb and remaining 1/4 cup of sugar in a large saute pan and cook on high, stirring constantly, until the sugar has dissolved, and the rhubarb has released liquid. Lower the heat to medium and cook the rhubarb until some of the liquid has evaporated, but the rhubarb still holds it shape and is firm. Remove from heat and pour rhubarb and any remaining liquid into the bowl with the berries. Add the balsamic vinegar and fold filling together.
Assemble the pie.
Preheat the oven to 400°F. Lightly and evenly spray a 9 x 13 x 2-inch metal pan with a cooking oil. If using, cut a piece of parchment paper large enough to fit into the metal pan with a good 2” hanging over the edge of the pan on either side of the long edge. Fit the parchment paper into the metal pan; the cooking oil should help anchor the paper to the pan.
On a well-floured surface, roll out one disc of the pie crust to a rectangle that is 15” by 11” in length. Carefully transfer it to the metal pan, with the sides of the crust going up all sides of the pan with an inch overhang. Carefully spoon in the pie filling into the middle of the pan, spreading the filling all the way around, and lifting the sides of the crust if they have fallen down, so that the filling is “inside” the crust. Once you added all the filling and evenly distributed around the pan, it should hold the sides of the pie crust up.
Roll out the second disc of pie crust to a 15” by 11” rectangle. Either cut the second crust into strips and “weave” a top similar to the classic apple pie or transfer the whole top crust to the pan, and tuck the edges of the dough into the side of the pan, on top of the bottom crust. Pinch the top edge of the pie all the way around to seal the pie crust, and then cut the top of the pie with a knife decoratively to give some steam vents.
Take the egg and water and beat them together with a fork until it starts to froth. Brush the top of the pie crust with the egg wash and then sprinkle the turbinado or white sugar on top.
Place pan on a rimmed baking sheet and bake in oven for 55 to 65 minutes, or until the filling is bubbling through the top crust holes or vents and the top of the crust is golden brown. If the crust is browning too fast and the filling isn’t bubbling yet, cover with aluminum foil to keep the top crust from burning.
Note: If you don’t have quick cook or baby rolled oats, place the same amount of regular or thick cut oats in a food processor or blender, and pulse until the oats have broken down into the size of tiny pebbles.