Beat the sugar, eggs and milk together. Combine the flour, red colouring (powder), cocoa powder and baking powder together and sieve. Melt the butter in the meantime. Add the dry ingredients to the egg mixture and combine to form a smooth batter. Add the melted butter to the batter and combine.
Combine the cream cheese and butter to form a light batter. Melt the white chocolate to 30 °C and add to the butter mixture. Combine and whip.
Melt the chocolate with the cocoa butter. Add the grapeseed oil and combine. Cool to 31 °C.
Prepare a 40 x 60 cm baking tray, place a silicon baking sheet on top and then a 39.5 x 59.5 cm metal rectangle, 4 cm high, in the tray. Pour the cake batter and spread to get an equal layer. Bake in a ventilated oven at 170 °C for 17 minutes. Cut the sides of the cake to release it from the metal rectangle. Remove the rectangle and place a sheet of baking paper on top of the cake. Place a grill on the baking paper and flip the cake over so the silicon sheet comes on top. Set aside to cool completely. Trim away 1 cm of the outside of the cake. Divide it into 3 equal parts of 19 x 38 cm. Cover the first layer of cake with 155 g of the cream cheese topping (about 1 cm thick). Spread to get a flat and equal layer. Lay the second sheet of cake on top and add another layer of cream cheese. Close with the last layer of cake. Store in the refrigerator for 1 hour. Trim away the outside of the cake. Divide into 7 cakes of 5 x 18 cm each and place on their side. Store in a freezer for 15 minutes. Dip them halfway into the melted white chocolate and place them on a baking sheet. Decorate the top of the cakes with a zigzag pattern using a St Honoré nozzle. Use the cut parts of the cake for the final touch. Cut them in 1 x 1 cm cubes and let them dry for 20 minutes at 50 °C. Place them on top of the Red Velvet cakes.
Red Velvet cakes can be stored frozen, with decoration, if well covered in plastic foil. When needed, move from the freezer to the fridge and keep covered until defrosted.