In the bowl of a stand mixer fitted with paddle attachment, mix butter with almond meal, sifted icing sugar and vanilla seeds.
Add lightly beaten whole egg and mix to combine.
Add the sifted flour and mix just to combine.
Flatten the dough into a round disc, wrap in cling film and refrigerate for 8 hours.
Heat diced marzipan in the microwave, to soften, add lemon juice and mix with a hand blender, then add vanilla powder.
Heat the mixture until 176F - 80°C and pour over colored melted chocolate.
.Mix with a hand blender until smooth.
Refrigerate about 12 hours.
Brush the interior of your ring with butter, 3.5 inches x 11.5, (9x29 cm), and place on a baking tray with baking paper (I used micro perforated round tart ring, micro perforated tray and Silpat non-stick mat).
Roll the dough gently until you have an even 3mm thickness
Gently ease the dough into the sides of the moul, use your fingertips to press the pastry into the edges and up the wall of the tin.
Using the knife, remove the overhanging pastry.
Prick the base with a fork and refrigerate for 2 hours
Heat fan oven to 320 F - 160°C.
Bake the tart shell for 22 minutes.
Brush the tart shell with melted cocoa butter and let completely cool.
Heat lemon juice until 176F - 80°C.
In a bowl, place sugar, egg yolks, whole eggs and mix to combine.
Pour the hot lemon juice over the mixture and cook, stirring constantly, until 180F - 82°C.
Out of the heat, pour the custard over the chopped white chocolate and cocoa butter and with a hand blender, mix to combine.
When the mixture reaches 122F - 50°C, add diced butter and mix to combine.
Pour the custard into the tart shell and let in the fridge for a couple of hours.
Pour the ganache in a pastry bag, fitted with a grass plain nozzle and pipe the ganache over the lemon custard.
Remove excess with a knife.
Decorate as you wish and serve.
Lemon and white chocolate Zéphyr Cacao Barry ganache
I used Chocolate by Valrhona.