1-Getting started: Begin by preheating your oven to 350°F (175°C) and lining two 8-inch or 9-inch round cake pans with parchment paper for easy removal later. This recipe guides you through each phase, ensuring your cake comes out just right every time.

2-Next, make the raspberry filling by combining 2 cups raspberries, ⅓ cup granulated sugar, 2 tablespoons cornstarch, and 1 tablespoon lemon juice in a saucepan. Cook this mixture over medium heat, stirring constantly until it thickens, then cool it completely and chill for at least 30 minutes. This step adds a burst of tartness that pairs beautifully with the sweet layers.

3-For the cake itself, sift together 2 ½ cups all-purpose flour, 1 tablespoon baking powder, ½ teaspoon baking soda, and ½ teaspoon salt to ensure even texture. In a large bowl, beat ½ cup softened unsalted butter, ¼ cup sunflower oil, 1 ½ cups granulated sugar, and 2 teaspoons vanilla extract until the mixture is pale and fluffy. Add 1 large egg and 2 large egg whites one at a time, mixing well, then incorporate ½ cup full-fat sour cream.

4-Gradually add the sifted dry ingredients to the wet mixture, alternating with ¾ cup whole milk, and beat briefly until just combined. Gently fold in 1 ½ cups fresh raspberries to keep them intact. Divide the batter between your prepared pans and bake for 25-30 minutes, or until a skewer inserted comes out clean. Let the cakes cool in the pans for 20-30 minutes before transferring them to a wire rack.

5-While the cakes cool, prepare the white chocolate frosting by heating ½ cup of the heavy whipping cream with vanilla bean seeds in a saucepan until simmering. Pour this over 12 ounces of chopped white chocolate, let it stand for 2 minutes, and whisk until smooth. Cool completely, then whisk in the remaining ¾ cup cold cream and chill for at least 2 hours. Once chilled, whip the frosting until fluffy and add 1 teaspoon vanilla extract if needed.

6-To assemble, place one cake layer on a plate, pipe a border of frosting around the edge, and spread the chilled raspberry filling inside. Top with the second layer, cover with the remaining frosting, and smooth everything out. Garnish with fresh raspberries for a final touch. Remember, accurate measurements help avoid common pitfalls like a dense cake.