1. To make the tart bases, blend the biscuits in a food processor until they become a fine sandy crumb, add the cocoa powder and icing sugar, and process until combined. 
2. Add melted butter and pulse until combined and mixture begins to clump together. 
3. Press the mixture evenly into the base and sides of six 12cm loose bottomed tart pans. Using a flat-bottomed glass or cup can help to press the mixture firmly into the pans. Use your fingertips to smooth down any edges. 
4. Depending on how tightly you pack the base, and the depth of the pans, there may be a little of the crumb leftover. Refrigerate tart bases for 30 to 60 minutes to firm up before adding the filling.
5. While the bases are chilling, make the berry coulis. Place the berries (chop the strawberries first if using), sugar and lemon juice in a small saucepan. Bring to a simmer and cook for 5 to 10 minutes until the fruit is soft and juicy. Crush the berries with a fork or the back of a spoon to make a sauce. 
6. Make a slurry with the cornflour by placing it in a small dish, add 1 teaspoon of cold water and mix to combine. Stir the cornflour slurry into the simmering coulis. Remove from heat and set aside to cool, the coulis will thicken a little as it cools.
7. To make the ganache filling, add the dark and milk chocolate Dotties to a medium sized bowl or jug. In the microwave, or a small saucepan over medium heat, bring the cream and butter to almost boiling point, stirring often to melt the butter. 
8. Pour the hot cream and butter mixture over the chocolate so that it is submerged. Leave to stand for five minutes to allow the chocolate to melt, then whisk the mixture until smooth and glossy. 
9. Pour mixture evenly over the chilled tart bases, leaving a small amount of room at the top for the coulis to be added. Drizzle 1 to 2 tablespoons of coulis over each tart in a circular motion, then using a toothpick, swirl gently to make a ripple. 
10. Refrigerate for at least four hours, preferably overnight, until set.
11. Remove from refrigerator 10 minutes prior to serving. Carefully remove the tarts from their pans by placing on the top of an inverted glass and gently pulling the side of the tin down. Warming the outside of the pans with your hands will help if they don’t come away easily to begin with. 
12. Remove the pan bases and sprinkle tarts with Koko Black Chocolate Shavings, top with extra Koko Black chocolates and fresh berries, and serve with double cream, any remaining berry coulis if you wish.

Note: If you have leftover ganache filling, it can be stored in the refrigerator and warmed to be used as a chocolate sauce.