1. Center a rack in oven and heat to 325 degrees. Press a single large piece of parchment into a 9x5" loaf pan, allowing excess to hang over long sides of pan.
2. Melt 6 tablespoons butter in a small skillet over medium-low heat and cook, swirling occasionally, until sputtering subsides. Continue to cook, scraping bottom of pan frequently, until butter turns golden brown and smells nutty, 5 to 7 minutes. Working quickly, scrape butter and browned solids into a heatproof bowl and let cool 5 minutes.
3. Whisk yogurt, granulated sugar, 1/2 cup packed brown sugar, egg, baking powder, vanilla, and 1/2 teaspoon salt in a large bowl until combined. While continuing to whisk, slowly add browned butter, including browned solids, until blended.
4. Using a rubber spatula, gently fold in 1 3/4 cups (8.75 ounces) flour until just barely combined, being careful not to overmix (batter will be very thick and have some lumps). Gently fold in 1 1/4 cups blueberries, then transfer to prepared pan and carefully spread into an even layer, pressing batter into corners. Scatter remaining 3/4 cup berries over top and gently press into batter.
5. Wipe out skillet, then add remaining 2 tablespoons butter and melt over medium heat. Remove from heat, add remaining 1/3 cup packed brown sugar, the walnuts, remaining 1/4 cup flour, the cinnamon, and a pinch of salt and stir until fully combined and clumps form. Spoon mixture evenly over top of batter and gently press to adhere.
6. Transfer to oven and bake until a toothpick inserted in center of cake comes out mostly clean (a few moist crumbs are okay), 60 to 70 minutes. (If streusel begins to turn very dark, loosely cover top of pan with foil.)
7. Cool in pan for 15 minutes, then use parchment overhang to lift cake out. Transfer to a wire rack and let cool completely, about 1 hour 30 minutes.
Source: Hannaford fresh Magazine, July - August 2019