Prepare the cake layers first. Preheat oven to 350F/177C. Prepare three, 8-inch cake rounds with parchment paper. In a large mixing bowl, beat together softened butter, sugar and vanilla for a few minutes until fluffy. Add the eggs, one at a time, and beat for 2 to 3 minutes until creamy and smooth. Next, pour in the milk (I recommend using warm milk).

In a separate bowl, combine all the dry ingredients: flour, baking powder and salt. Sift the dry ingredients into the cake batter and whisk by hand to avoid over-mixing the batter. Add the lime zest and stir again. Divide the cake batter evenly between the prepared pans and add 6 to 8 whole blackberries onto each layer. Bake in preheated oven for 28 to 30 minutes, or until a toothpick inserted into the center comes out clean. Allow the layers to cool completely, then level off the tops using a long serrated knife.

While the layers are baking, prepare the lime curd. In a large mixing bowl, combine the eggs, egg yolks and sugar. Whisk vigorously for 3 to 4 minutes until the mixture is light and ribbons off the whisk; a hand mixer works well here, too. Strain the freshly squeezed lime juice of pulp, then add to the mixture. In a small ramekin, combine the cornstarch and water, then add the slurry to the mix. Add a few drops of green food coloring, if desired.

Pour the lime curd base into a medium-sized saucepan. Cook over medium heat, stirring constantly with a rubber spatula, until the curd thickens. As it cooks, it will start to form clumps; use a whisk to break up any clumps. The curd is ready when it holds its shape on the back of a spatula. Remove the lime curd from heat, cover with plastic wrap and refrigerate until completely cooled.

Prepare one portion of the 'Berry Whipped Cream Frosting' using 1 cup blackberries in place of the raspberries as shown in the video recipe. Place a few cups of the frosting into a piping bag tipped with a simple round tip or a French star tip.

To assemble the cake, spread a bit of frosting onto each layer, then pipe a generous barrier border of frosting around the edge; this will keep the lime curd from coming out the sides of the cake. Add a generous amount of lime curd into the center, then top with next layer. Frost the top and sides of the cake, then garnish the top with dollops of cream, fresh blackberries and small flowers, if desired. Keep cake refrigerated if not serving right away.