Have never done any mustard sauce ( senapsås) but the only powder in can find in any Swedish supermarket webshop is Colmans-Dry-Mustard-Powder the like is to one seller of it on US Amazon. Most recipes I can find online use premade mustard but some use mustard seeds that US amazon had a lot of.
The mustard in most recipes is Skånsk snap so a variant with lot of black mustard seeds. I have no idea if there is any equivalent mustard in US stores. Some use french mustard like Dijon mustard that looks like it exists in the US too.
She clearly states that it is dry Colman's mustard. "Mix up this dry Colman's mustard."
You just stir in some water.
Interesting. I'm a fan of Coleman's mustard. The pre-made stuff is pricey, but I get the dry stuff. It's as spicy as horseradish, but in a very mustardy kind of way. They're close relatives, so it's just like a spiced horseradish.
But here's the kicker: instead of water or vinegar to mix the dry mustard, I use Cajohn's Magma hot sauce which has almost zero flavor, and is pure heat. It's literally vinegar with capsaicin extract.
So you've got two levels of heat. It's amazing!
Which of the 3 was your favorite topping?