Whisk together the warm milk, warm water, sugar and 2 tablespoons melted butter in a mixing bowl until the sugar has dissolved. Sprinkle yeast over top and set aside for 5 minutes.
Once the yeast is foamy stir in the flour adding more if needed to make a stiff dough. When the dough has pulled together turn it out onto a lightly floured surface and knead until smooth and elastic; about 8 minutes. Place into an oiled bowl then cover with a cloth and let stand in a warm place until doubled in bulk; about 1 hour.
Combine 1/2 cup sugar with the cardamom and cinnamon in a small bowl; set aside. Punch down the dough and turn it out onto a lightly floured surface. Roll the dough into a 20 x 36 cm rectangle and brush with 125g of melted butter. Sprinkle with the cardamom sugar, sultanas and walnuts. Roll into a log then pinch the edges closed and place onto a baking paper-lined baking tray. Cover with a cloth and let stand in a warm place until doubled in bulk; about 1 hour.
Preheat an oven to 180 degrees C.
With a sharp knife score the top layer of the scroll with V-shapes that don't quite meet in the middle the whole length of the scroll, this will make the scroll look braided and is very pretty but could be skipped. Whisk the egg with 1 tablespoon of water in a small bowl. Brush the egg wash over the top of the scroll. Sprinkle with almonds and Demerara sugar.
Bake in the preheated oven until the scroll is golden-brown and sounds hollow when tapped on the bottom, 30 to 35 minutes. Cool completely on a wire rack before slicing.