In a medium pot, dissolve 6 ounces (170g) of sugar in water over medium heat. Add butter. Stir frequently and remove off heat once the butter dissolves.
Add ground biscuits to the mixture and stir well until integrated. Grind your nuts to flour consistency and add to the batter. (Alternatively, if you bought them ground, add them to the batter right away.) Mix well until you get a thick, even, sticky mixture. Divide the batter in two and place into separate bowls.
Make a water boiler by filling a medium-sized pot ⅓ with water and bringing it to a boil on high. Bring the temperature down to low. In a medium-sized bowl (or a smaller pot) that fits snuggly in the pot with water, put chocolate and 1 ounce (30 grams) of butter. Stir well while chocolate and butter melt. As soon as they do, remove them from heat.
Pour ½ of the melted chocolate into one of the bowls with the batter and mix well until integrated. Add rum (vanilla) to the other half of the batter. Mix well until integrated.
In a greased pan, spread the batter portion with chocolate on the bottom. Use your fingers and/ or a spatula to distribute it evenly in the pan. Place the batter portion with rum (vanilla) on the top of the first. Spread it out over the first layer the best you can with your fingers, and then flatten it with a spatula. (Work fast as it'll be sticky.) Finally, top everything with the other half of the melted chocolate. Use a spatula to even it out and flatten the top.
For best taste, cover with foil and transfer to the fridge for an hour. After this time you can cut the entire bajadera into bars right away, or keep it in the pan and cut before serving.
Serve 1-3 bars along with some coffee, elderberry juice, or a drink of choice. For the best taste and easier cutting, take bajadera out of the fridge 15-20 minutes before serving. Store in an airtight box (or foil) in the fridge or a cool, dark place for up to 5-7 days. Freeze - if planning to freeze bajadera, do so after it cools down, but before you cut it into bars. Wrap it in freezer foil or freezer bags, getting out as much air as possible to prevent freezer burn. Once you plan to eat it, take it out and let it thaw until it's almost room temperature. Cut it into bars and serve.