1-First Step: Gather and prep (Mise en place) * Preheat your oven to 325°F and line a 9×9-inch baking pan with parchment paper so you can lift the bars out easily for slicing. Lightly grease the pan if the parchment does not fully cover the sides. * Chop the 6 ounces white chocolate bar into small, even pieces so it melts evenly. Cut 10 tablespoons unsalted butter into pieces for quicker melting. * Measure 1 1/4 cups granulated sugar, 1 3/4 cups all-purpose flour, 1 teaspoon salt, and 1/4 teaspoon baking powder into separate bowls for quick mixing.

2-Second Step: Melt butter and white chocolate * Place the butter pieces and the chopped white chocolate bar in a microwave-safe bowl. Melt in the microwave in 20-second increments at medium power, stirring between each burst until smooth. Use short bursts to prevent graininess or seizing. If the mixture thickens, stir gently until glossy. Alternatively, use a double boiler over simmering water and stir constantly until melted. * Let the melted mixture cool slightly while you prepare the eggs and sugar.

3-Third Step: Whisk sugar and eggs * In a clean bowl, vigorously whisk the 1 1/4 cups granulated sugar with 2 large eggs plus 1 egg yolk until the mixture is pale yellow and slightly thickened. This step helps create shiny, crackly tops and adds structure to the bars. * Stir in 1/2 teaspoon vanilla extract, then pour the slightly cooled melted white chocolate and butter into the egg-sugar mixture. Stir gently to combine until uniform.

4-Fourth Step: Combine dry and wet ingredients * Whisk together 1 3/4 cups all-purpose flour, 1 teaspoon salt, and 1/4 teaspoon baking powder in a medium bowl. Sift if you prefer a smoother batter, but gentle whisking is fine. * Fold the dry ingredients into the wet mixture with a spatula. Mix until just combined avoid overmixing to keep the bars tender. * Fold in 1 cup white chocolate chips for extra pockets of melty goodness. If adding 1 cup chopped walnuts for texture, fold them in now as an optional step.

5-Fifth Step: Bake * Spread the batter evenly into the prepared 9×9-inch pan using a spatula to smooth the top. Tap the pan gently on the counter to release any large air bubbles. * Bake at 325°F. The recipe’s summary lists 40 minutes baking time, and many bakers find that 40 minutes is a good guideline. The directions also note baking for 42 minutes; check around 40 minutes and plan for 40 to 42 minutes total. Insert a toothpick near the center: it should come out clean or with moist crumbs (not wet batter) when done. * Oven temperatures and metal vs glass pans affect time: metal pans conduct heat more evenly than glass, which may change the bake time by a few minutes. If using a glass pan, check a few minutes earlier to prevent over-browning.

6-Final Step: Cool and serve * Allow the white chocolate brownies to cool completely in the pan before slicing. Full cooling prevents gooey centers and helps you get clean slices. For quickest clean removal, lift the parchment paper out of the pan and slice on a cutting board. * Store finished bars in an airtight container at room temperature for up to 5 days, or follow the storage methods in the storage section below for longer keeping.