Egg yolk feather swirl bar

Method

1. Make the tools

   Straighten a wire coat hanger, bend one end up as a handle, and thread drinking straws onto the wire to cover a straight run as long as the inside of the mould less 1 cm; then bend the other end up as a second handle. The straws thicken the wire for a bolder feather. Cut two strips of stiff card as long as the mould and 2 cm taller, and wrap them in packing tape.

2. Get ready

   Put on goggles, gloves and long sleeves and open a window. Line the mould and set it level where it can stay, with the dividers, the hanger, three small jugs and four squeeze bottles in reach.

3. Separate the yolks

   Let 2 large eggs come to room temperature, separate them and keep the whites for the kitchen. Weigh 60 g of the recipe's olive oil into a cup and whisk the yolks, about 36 g, into it. Wash your hands and the bowl.

4. Disperse the colours

   Weigh the sweet almond oil and take 42 g of it. Stir the titanium dioxide into 36 g in a jug, and the ultramarine pink, the ultramarine violet and the chromium green each into ½ teaspoon (2 g) in its own small jug, until smooth.

5. Make the lye solution

   Where the air moves, pour the 125.6 g of sodium hydroxide slowly into the 274.1 g of water, never the reverse (the yolks bring about 19 g more), and stir until clear. Leave it labelled and out of reach to cool to 32 to 35 °C (90 to 95 °F).

6. Melt and scent the oils

   Melt the coconut oil, cocoa butter and shea butter, stir in the canola, avocado and castor oils and the rest of the olive and almond oils, and let them cool to 32 to 35 °C (90 to 95 °F); much cooler, and the butters start to thicken the batter. Stir in the lavender and litsea oils.

7. Blend to very thin trace

   Pour the lye solution in down the blender shaft, tap out trapped air, and blend in short pulses only until the batter is smooth and opaque, thin as single cream.

8. Add the yolks

   Pour the yolk and oil through a sieve into the batter and whisk them in by hand. Keep the batter thin from here on: the layers need time.

9. Colour the portions

   Pour about 55 g of batter into each small jug and whisk them pink, violet and green. Whisk the white into the batter left in the pot and set about 300 g of it aside in a jug for the top.

10. Pour the base and set the dividers

    Pour white into the mould about 1.2 cm deep, some 270 g, then push the two dividers into it lengthwise, 3 cm apart down the middle, and tape a tab from each end to the rim.

11. Stack the middle

    Fill the squeeze bottles, one with each colour and one with white from the pot. Squeeze a thin layer of green into the centre channel, then white, pink, white, violet and white, and go round again until the centre is about 3.5 cm deep, keeping a tablespoon of each colour back. Gaps in a layer are fine.

12. Fill the sides

    Pour white into the two outer channels, a little on each side in turn so the dividers stay upright, until they reach the depth of the centre.

13. Lift the dividers

    Untape the tabs and pull the dividers straight up, slowly, one at a time.

14. Draw the feather

    Push the hanger straight down through the middle of the coloured layers until the straws lie on the bottom along the whole length. Slide it across the bottom to one side, draw it up that wall and lift it out.

15. Top it

    Whisk the reserved white and pour it gently over the top in a back-and-forth pattern. Squeeze a green squiggle down the length, a pink dot in each curve, and a smaller violet dot on each pink one.

16. Leave it uncovered

    Mist the top with alcohol, away from any flame, and leave the mould uncovered in a cool room for 24 to 48 hours, with no towel, so the loaf stays cool and does not gel.

17. Unmould and cut

    Unmould with gloves on once firm, usually after 2 days, and cut bars about 2.5 cm (1 in) thick: each shows the coloured layers pulled down into a feather through its middle.

18. Cure

    Stand the bars on edge with air between them, out of direct sun, for 6 weeks, turning them every few days.