Unagi eel mousse:
Heat cream, milk, unagi sauce to 40 degrees then blend with kuzu for 3 minutes on low speed.
Add the smoked eel fillets, vinegar and salt and blend on high until smooth , pass through a chinois
Return to the pan and bring to a simmer stirring constantly, decant while hot into a piping bag
Line the sand eel up on baking parchment and pipe the mouse over the sand eel so the head and tail are still seen , fridge
Pastry:
Roll the butter into squares between parchment to the thickness of 7mm and refrigerate
Weigh all other ingredients into a dough mixer and knead for 5 minutes on medium speed until fully incorporated
Leave dough in the fridge over night
Roll dough to a thickness of 7mm and place butter in the centre of the dough, folding the dough over the butter until covered
Roll to 7mm again but this time do a book fold with the dough. Repeat this step again then refrigerate for 30 min
Roll dough to a 3mm, cut into 4cm by 10 cm rectangles
Place two frozen sand eels and mousse on the top and bottom of the rectangle then roll into a pain au chocolat shape
Prove the pain au unagi until doubled in size in a warm place on a baking tray
Unagi glaze:
Mix 50/50 egg yolk and unagi sauce until smooth
Assemble:
Preheat the oven to 180 degrees
Brush the glaze over the pain au unagi and bake for 25 min