Preheat oven to 350°F. Grease, line with parchment, butter and flour two round 5-inch pans.

In a medium bowl or measuring cup, combine and stir the egg whites, egg, 2 tablespoons of the milk and emulsion (or vanilla). Set aside.

In the bowl of an electric mixer fitted with the paddle attachment, combine the dry ingredients, including the sugar, together on low speed (I use the “stir” setting on my mixer) for 30 seconds.

Add the butter and shortening, and blend on low speed for about 30 seconds, then add remaining milk, and mix on low speed until just moistened. Increase to medium speed and mix for 1-1/2 minutes.

Scrape the sides of the bowl and begin to add the egg/milk mixture in 3 separate batches; beat on medium for 20 seconds after each addition.

Divide the batter in two, spreading it evenly with a small offset palette knife. If you have a kitchen scale, weigh the batter in the pans to ensure 2 even layers (they should each weigh about 270 g).

Bake 20-25 minutes or until a cake tester comes clean when inserted into the center. Be so careful to not over-bake. Check cake at 20 minutes, but not before, and once you feel it’s almost ready, set the timer for 2 minute intervals.

Let cool on racks for 10 minutes before loosening the sides with a small metal spatula, and invert onto greased wire racks. Gently turn cakes back up, so the tops are up and cool completely.

In a small saucepan over medium heat, combine 1-1/2 cups of the blackberries, sugar, orange juice and salt until the berries start to break down, stirring often, about 10 minutes.

Lower the heat and simmer until compote coats a spoon, about 15 minutes.

Remove from heat and let cool down slightly. Using an immersion blender (carefully) or counter-top blender, pulse until smooth. Push compote through a fine mesh sieve into a clean glass bowl and discard the seeded pulp from the sieve. Stir in remaining fresh blackberries. Keep covered and chilled for up to 3 days.

In a small bowl, place the cold water and sprinkle with the gelatin. Let sit for at least 10 minutes. In a small saucepan, bring 1/3 cup of the cream just to a simmer, then stir into the gelatin mixture. Refrigerate, stirring frequently, until cool but not set, about 8 minutes.

In a chilled stainless steel bowl with a chilled whisk attachment (for stand mixer), beat the remaining whipping cream, icing sugar, vanillla and salt until it thickens just slightly and soft peaks begin to form, about 1 minute. Very gradually add the gelatin mixture and continue beating until medium-firm peaks form (should be thick enough to spread). In a large bowl, soften mascarpone and gently fold in whipped cream mixture. Keep covered and chilled until ready to use.

In the bowl of an electric mixer fitted with the paddle attachment, whip butter for 8 minutes on medium (I use “4″ on my KitchenAid). Butter will become very pale & creamy.

Add remaining ingredients and mix on low speed for 1 minute, then on medium for 6 minutes. Frosting will be very light, creamy and fluffy. Separate into 3 bowls and tint with your favourite gel paste colours. Best used right away (for ideal spreading consistency).

Cut your 2 cake layers each once horizontally with a long, serrated knife, so you have a total of 4 layers. Place your first cake layer, face-up, onto a small plate or cake stand (or 5-inch round foil cake board).Fill your pastry bag with about a cup of the Whipped Vanilla Frosting (un-tinted) and pipe a dam around the perimeter of the cake layer (this will keep our compote and Whipped Mascarpone Filling in place). Spoon a few tablespoons of the compote and berries inside of the dam, along with a few tablespoons of the whipped filling. Gently spread the filling using a small offset spatula.

Repeat until you come to your final cake layer, which you will place face-down. If you find the cake too soft and unstable, put in refrigerator for a few moments to firm it up, then resume. If you see any spots where the compote is peeking through or starting to ooze out (ahh!), use your piping bag to squeeze more frosting over it, between the layers. Use your clean offset spatula to carefully smooth the frosting so it's flat against the cake.

Cover the entire cake gently with plastic wrap (I like Press n' Seal), and then, once covered, use your hands to carefully ensure the cake is lined up straight and flattening any lumps or bumps of frosting. Chill for at least 30 minutes.

Once cake is stable and chilled, apply an even layer of frosting to the entire cake, to seal in crumbs. Chill again until frosting is firm, about 30 minutes (at least). While the cake is chilling, you can divide remaining frosting into 4 small bowls, and tint 3 of them with your soft gel paste. Keep one bowl of frosting un-tinted.

Place cake plate/board with cake onto a turntable, if possible. Be sure your frosting is smooth and fluffy, working it with a rubber spatula for a few moments. You can even warm in microwave for a few seconds to soften it up. Apply a thick layer of your darkest colour to the bottom third of your cake, then another above it over the middle of the cake, and finally your final colour of frosting all over the top and upper third of cake. Add the un-tinted frosting in a few areas, to add interest. Using a metal spatula blend the colours together by smoothing frosting all over cake, as you would a typical one-colour cake. Be careful to not overblend. For textured effect (as in photos) you can use a small metal spatula, holding it with one hand on an angle starting at bottom of cake, keeping it fairly still, move the turntable with the other hand, slowly letting the spatula move up slightly with every turn.