Begin by grinding the saffron in a pestle and mortar. Pour the milk into a small saucepan then add the saffron. Heat the milk with the saffron to 38°C, remove from the heat and add the fresh yeast if using and stir to incorporate with the milk. Place the flour, (dried yeast if using), sugar and salt in the bowl of a free standing mixer with the dough hook attached. Add the milk mixture with the motor running. Mix until a dough forms on a slow speed. Once the dough has come together add three quarters of the egg and gradually add the butter, increase the pace to medium/high and work the dough for another 5-8 minutes or until it feels shiny and smooth, you may need to add a tablespoon of flour if the dough is too loose.
Place the dough in a bowl and cover with a tea towel and let it rest for 20-30 minutes to rest.
Mix the ground almond, butter, vanilla extract and caster sugar until you have a smooth paste, set to one side.
When the dough is ready divide it into two. Roll each each one into a rectangle on a lightly floured surface. They should be approximately 25-30cm long and 15-18cm wide. Spread an even layer of filling on the surface. Drain the water from the raisins and sprinkle on the the filling if using. Roll into a log lengthways. Transfer the logs to a baking sheet lined with parchment paper, with enough room each side baring in mind they will double in size.
Now take a sharp pair of scissors and cut down the centre of the log, pushing the ‘v’ shape to either side. (See diagram). Cover with a tea towel and leave it to rise for approximately 45 minutes or until almost double in size. Meanwhile, heat the oven to 180°C. Brush with the remaining egg and sprinkle with sugar nibs if you have omitted the raisins. Bake for approximately 20-25 minutes or until it’s golden brown in colour. Cool on a wire rack. Serve warm with coffee.