<PERSON> is indeed a character from the original Vertigo series, published as part of DC's darker, grittier comics.
<PERSON>, the show forerunner and executive producer (along with <PERSON> and <PERSON>) have conceded that they could not do a one-to-one translation from comic to episode as that would make the series end rather quickly. We cannot rely on canon for an answer here, more than likely, as there only about 75 issues in total with 4 specials and a spin-off series.
My opinion (and I will try to defend it) is that this is yet another nod to "The Big Lebowski" (<PERSON>'s least favorite film by the <PERSON> Brothers). Towards the end of that film (no spoilers, hopefully), we are introduced to a group of individuals who dress in black and simply call themselves Nihilists because "They believe in nothing".
The connection to <PERSON> may be tenuous but the similarities are the following:
* German origins - The Nihilists are of German descent and we know <PERSON> initially serves a German government agency.
* Accent - just because someone is of German descent does not automatically mean they're gonna have a German accent. The choice to give both pronounced German accents is deliberate (a TVTrope, if you will).
* Philosophy - the comments to the question are what prompted this answer as there are references to sadism, which is the enjoyment of inflicting pain. In a romantic setting, it requires the consent of another party who enjoys receiving pain in a BDSM arrangement (as poorly portrayed in Fifty Shades of Gray). This, however, is not what is taking place in this scene. <PERSON>, per the OP, is regaling Herr <PERSON> with a story about meaning, which is the antithesis to Nihilism. In asking her to remove her top and stick the butter under her chin, he is showing that a) he has no interest in her story b) demonstrating that his actions won't always have a purpose (as he might not believe in anything either) c) as someone who doesn't believe in things like morality or propriety, actions that might be deemed cruel to a casual observer are part and parcel to any conversation with him.
There are no pointless scenes in television, every minute (indeed every second) is paid for in actor salaries, wardrobe, makeup and post-production. 663
Whether the choices that are made make sense to each of us individually or to the audience as a whole is another topic altogether.
Update after re-watching scene
This scene occurs in the Herr Star chronology after he's shown the video of <PERSON> using the voice of God super-power on <PERSON>, telling her to "Sleep" Everything else said above still stands, but with the additional context of <PERSON> being unimpressed with the footage, saying he's bored (after the floating pig incident) "Since when is a woman obeying a man a superpower?". The dinner scene then is him proving his own point. Power is not always supernatural, the daughter of the governor of Louisiana felt like she had to listen to what he said as he worked for the world's most powerful organization, with agents in 113 countries, all ready to do his bidding at a moment's notice. Would you refuse what he said?
Next on the chronology, we do hear about his R-word fantasy with multiple prostitutes but through his battle with Cat popup ads, he accidentally reviews more of <PERSON>'s surveillance footage.
Once again, everything above stands but perhaps <PERSON> is a bored Nihilist searching for the same thing <PERSON> is - order in a world of chaos.
One more update - within the larger context
I am getting tired of the phrase Nihilism because it's a weird word to type, like bananas, too many of the same vowel- I digress.
In their initial date, mentioned by the OP, <PERSON> was more than bored. He was baffled perhaps even offended by her story, perhaps the way she told it. The conversation starts with how important <PERSON> is and how his influence got them a reservation at a restaurant that was closed other than the two of them (and the staff, of course). <PERSON>, impressed with his masculine power/influence, tries to regale him with her feminine accomplishments of traveling and volunteering but it is the way she tells it that offends him. She begins with a condescending tone of someone who has achieve enlightenment and has to teach the ignorant "The Way" or some such ("I was once like you were..."). Indeed, what triggers the sequence of events that started this question and its lengthy answer (I'm sorry... 663