Prepare the dry mix ingredients. Grind the flax seeds in a coffee grinder until they turn into a fine meal, but do not grind the sesame seeds. You can lightly toast the sesame seeds in a dry pan to bring out a deeper nutty aroma. Crush the walnuts in a mortar or with a rolling pin, stopping before they become powder so you still have small crunchy pieces throughout the salami.
Break the biscuits into pieces and place them in a food processor or a large bowl. Aim for irregular chunks rather than fine crumbs so that you keep a nice texture in the final dessert.
Combine everything to finish the dry mix. Add the crushed walnuts, ground flaxseed and whole sesame seeds over the biscuits and mix well until all the pieces are evenly distributed.
Add the cocoa powder last. Sprinkle the cocoa evenly over the dry ingredients and toss or stir until the biscuits and nuts are lightly coated and no visible white patches remain.
In a separate bowl or small saucepan, melt the butter until fully liquid but not browned. Stir the melted butter into the sweetened condensed milk until you get a smooth, glossy mixture. Pour this sweet, sticky liquid over the dry ingredients, making sure to cover as much of the surface as possible.
Knead the mixture with your hands until everything is well combined and the “dough” looks even. The mixture should feel dense, elastic and pliable, slightly sticky but easy to shape without crumbling or falling apart.
Lay a sheet of plastic wrap (cling film) on the work surface. Place the mixture horizontally in the center and shape it into a long log, similar to a salami. Roll it tightly in the plastic wrap, smoothing it as you go, until you get an even, well-packed cylinder as shown in the pictures.
Refrigerate the dessert for 2–3 hours until firm. For faster chilling, you can place the salami in the freezer for about 20 minutes. Once set, the chocolate salami is ready to slice and serve, and it can be stored in the fridge for up to 4 days.