In a literal translation it would be, but considering it’s not a big bang, but the big bang, it’d be “Urknall” which I’m not sure how best to literally translate to English, but it’s something along the lines of “bang of origin” or “original bang”.
That doesn’t make the tweet any less wrong though, this is just semantics.
In terms of 40K recipes, corpse starch is pretty easy. De-bone a (generally human, but others can work in a pinch) corpse, grind up the rest, add salt, and pack it in a can.