That was a brave attempt, though!
I’m not sure how it works with that format of cacao. But when I’ve used the cacao powder for a hot chocolate drink, I’ve heated milk in a mug in the microwave (almond milk with just a little dairy milk) - then added a large teaspoon of cacao powder and 1-2 sachets of Natvia or xylitol (probably 1/2 to 1 tsp sugar substitute). Also sometimes a sprinkle of cinnamon, on top, as that tastes quite sweet.
With the cacao block, it sounds like it’s about creating a solution or paste. Which sort of reminds me of Camp coffee (without the sugar!) So maybe it’s about the ratios - using less of the boiled cacao solution and more milk type stuff. I use mostly almond milk as I think it has lower carbs than dairy. Maybe coconut milk would also be an option (as in the cartons of the version you’d put on cereal - not the cans of cooking product for curries!)
Hope you won’t give up on this yet. Even Formula 1 drivers would have had to practice a while, to manage a few smooth circuits eventually...