1. Prepare the crust. Pulse flour, sugar, and salt in a food processor to combine. Scatter butter over mixture and pulse until it resembles coarse crumbs. Add 5 Tbsp. water and pulse until mixture just holds together when pinched, but is not fully cohesive, gradually adding 1 tsp. of water at a time if needed. Alternatively, use a fork or pastry blender to combine.
2. Pour mixture onto a work surface and shape into a mound. With the heel of your hand, sharply press down and away on a small portion of the dough mixture, smearing it across the work surface; continue down the mound, little by little, until all the mixture has been smeared into a separate pile. Gather mixture into another mound and repeat smearing process. Transfer dough to a piece of plastic wrap, knead until cohesive, pat into an 8-inch disc, wrap, and refrigerate until very firm, about 1 hour.
3. Meanwhile, start the filling. Toss strawberries, rhubarb, and 1/3 cup of the sugar in a strainer set over a bowl; set aside to drain for 1 hour; discard the juices or reserve them for another use.
4. When ready to bake, adjust oven rack to the lower-middle position and preheat oven to 400 degrees F. Rest dough at room temperature for 5 minutes. Lay a large piece of parchment on work surface, dust with flour, place dough in center, dust top of dough with flour, and place a large piece of plastic wrap over it. Roll dough into a 14-inch-diameter circle about 1/4 inch thick; remove plastic and slide parchment sheet with dough circle onto a rimmed baking sheet.
5. In a large bowl, stir together cornstarch, vanilla, and orange juice. Add drained strawberry-rhubarb mix, orange zest, remaining 1/3 cup sugar; toss to combine well. Pour filling into center of rolled dough, leaving a 3-inch border around the edge. Fold dough over about 2 inches of the filling, working your way around the galette, overlapping the dough every 2 to 3 inches; gently pinch the pleated dough to secure it. Brush dough with egg and, if desired, sprinkle with sugar.
6. Bake until crust is golden brown and filling is tender, 30 to 35 minutes. Cool galette on baking sheet to room temperature on a wire rack. Transfer to a serving platter.
Source: Hannaford fresh Magazine, March - April 2015