Milk Chocolate Earl Grey Tart with Ombre Dark Chocolate Swiss Meringue Buttercream

CHOCOLATE SUGAR COOKIES

1. Preheat the oven to 350˚f /180˚c. Line two baking sheets with parchment paper. In the bowl of a stand mixer fitted with the paddle attachment, cream the butter and sugar until it is light and fluffy, approximately 5 minutes. Add the egg and vanilla paste, and beat until combined. Scrape down the sides of the bowl with a rubber spatula.
2. In a small bowl, sift together the flour, cocoa powder, baking soda and salt. Add the dry ingredients, and mix until well combined. Scrape bowl again to ensure that the ingredients are evenly incorporated.
3. Place approximately a cup of sugar in a bowl. Scoop tablespoons of the mixture using a #70 scoop, and roll into balls. Roll each ball in the sugar to coat completely. Place evenly spaced apart on the baking sheet, leaving room for spreading (11 per half baking sheet works well). You will need to bake your cookies in several batches.
4. Bake the cookies for 8-9 minutes, until puffy and barely golden around the edges. Remove from the oven and allow to cool for 5 minutes on the pan - during this time they will deflate and crackle slightly. Transfer to a cooling rack and allow to cool completely. Repeat sugar rolling and baking process with remaining dough.

CRUST

1. Place the cookies in the work bowl of a food processor and blitz until it resembles fine crumbs. Transfer to a bowl and add the melted butter. Stir well to combine. Press into the bottom and sides of a rectangular 14" x 4" removable bottom tart tin, using a drinking glass or measuring cup to compact down. Transfer to the fridge while you prepare the filling.

FILLING

1. In a medium pot over medium heat, heat the heavy cream until just shy of a simmer. Add the tea leaves, stir well, and leave to steep for 10 minutes. Strain, pressing down on the tea leaves. Re-measure the cream, and top up to 1 cup and 2 Tbsp if needed. Return to the heat and heat to just shy of a simmer.
2. While the cream is heating, place the chocolate and butter in a heatproof bowl. Once the cream is hot, pour over the chocolate and butter, and immediately cover the bowl with a plate. Leave to stand for 7-8 minutes, then whisk well. It will look curdled to begin with, but will quickly turn into a smooth ganache. Whisk until completely smooth. Pour the filling into the chilled tart crust, and tap to remove any air bubbles. Place in the fridge to firm up for 1 ½ to 2 hours. 

SWISS MERINGUE BUTTERCREAM

1. Fit 4-5 piping bags with french star tips of different sizes. 
2. Place the egg whites, sugar and salt in the bowl of a stand mixer or a heat proof bowl. Place over a pot of simmering water, ensuring that the water does not touch the bowl. Heat, whisking constantly, until the mixture registers 160˚f / 70˚c on a thermometer and the sugar has dissolved. Carefully transfer the bowl to the mixer, and fit with the whisk attachment. Whip the egg whites on high until they are snowy white and fluffy, 8-10 minutes. Add the butter one chunk at a time. The mixture may look curdled - but just keep mixing! Once all the butter is incorporated, mix on high for a further 10 minutes. Add the vanilla and mix until incorporated.
3. While the buttercream is mixing, melt the chocolate in a small heatproof bowl in 30 second increments in the microwave.
4. Remove about ¼ of the buttercream, and place into one of the piping bags. Add about half of the melted chocolate, and mix to incorporate. Remove ⅓ of the buttercream from the bowl, and place into the second bag. Add the remainder of the chocolate and mix to combine. Transfer half of the remaining buttercream to a third piping bag. Sift in the cocoa, and mix well. Transfer the rest of the buttercream to the fourth bag.
5. Pipe blobs of varying size on the surface of the tart, leaving it as sparse or as filled in as you like. Transfer to the fridge to allow the buttercream to set slightly. Allow to stand at room temp for 15 minutes or so before slicing and serving. Store leftovers in the fridge.