Preheat the oven to 350F/177C. Line three, 8-inch cake pans with parchment paper and spray the sides with a baking spray.
Prepare the cake layers first. Pour the buttermilk and cooking oil into a large mixing bowl and add the sugar, eggs, and vanilla and peach extracts. Mix on medium speed for a few minutes until the eggs are well beaten. In a separate bowl, combine the dry ingredients: flour, baking soda, baking powder and salt. Sift the dry ingredients into the wet and then mix on medium speed for about 1 minute, just until the dry ingredients are incorporated.
Divide the cake batter evenly between the three pans; use a kitchen scale for accuracy, if desired. Gently press the fresh raspberries into the cake batter, spacing them evenly apart.
Bake the cake layers in the preheated oven for 24 to 26 minutes, or until a toothpick inserted into the center comes out clean. Remove the cake layers out of the pans and onto a wire rack to cool completely.
Prepare the diced peach filling next. Dice the peaches into pea-sized pieces, then pour the peach and raspberry liqueur over the fruit. Let the peaches stand at room temperature, tossing every 15 to 20 minutes until ready to use.
Next, prepare a batch of either my ‘Raspberry Buttercream’ or my ‘Raspberry Whipped Cream Frosting’ recipe, both are linked in the post above. For the whipped cream frosting, prepare the raspberry sauce first. Place the berries and sugar into a small saucepot and heat over medium heat, simmering for about 6 to 8 minutes, until a jam forms. Press the jam through a fine mesh strainer to remove the seeds, leaving a smooth raspberry sauce. Allow the sauce to cool.
In medium bowl, whisk the softened mascarpone for about a minute, until smooth. Melt the white chocolate chips in the microwave, then immediately add to the cheese and mix again until smooth. Don't let the chocolate cool! Add the berry sauce next and mix until smooth. In a separate bowl, whisk the heavy cream and confectioner’s sugar for 3 to 4 minutes on high speed until stiff peaks form.
Add the cheese, chocolate and berry mixture to the whipped cream, along with a few drops of red food coloring. Whisk for a minute on high speed, until the frosting is smooth and creamy. Keep the frosting refrigerated until ready to use.
To assemble the cake, first make sure the cake layers are completely cooled! Use a serrated knife to level the top of each cake layer. Drain the liqueur from the diced peaches into a separate bowl. Use a pastry brush to lightly soak each cake layer with the liqueur.
Transfer about 1 cup of the frosting into a pastry bag tipped with a simple, round tip. Pipe a barrier ring of frosting around the edge of the cake layers; this will help keep the peaches inside the cake. Fill the center with a layer of diced peaches. Watch my video recipe to see how it’s done!
Frost the next cake layer with a generous amount of frosting, then invert the frosted side on top of the peaches. Continue assembling the cake, then frost the top and sides of the cake with a crumb coat of frosting. Chill the cake for 30 minutes in the refrigerator, then apply the final coat of frosting.
Garnish the top of the cake with fresh raspberries, sliced peaches and edible flowers, if desired. The cake is ready to be enjoyed right away. Keep it refrigerated if not serving right away.