vegan conversion ceremony
This is when one person has chosen the noble and delicious path of veganism for themselves, but refuses to keep this amazing secret to themselves and thrusts their food choices on others whenever they have a captive audience, such as when you are invited to their home for a meal or even a special event. The masterstroke is when you offer to bring non-vegan food so that 100% of the other people attending can have a choice, the vegan's conversion ceremony will not be disrupted, so there shall be no non-vegan food welcomed at all. The double masterstroke is when you ask "what can I bring?", the answer is a vegan dessert, even though you could not possibly bring your favorite vegan dessert from any familiar place since you have never ordered a vegan dessert in your life!

When you arrive, the noble vegan will use familiar words, such as butter, cheese, meatloaf, chicken; no they are not taunting you. None of these items are anywhere in sight and none will be served. Your host may be performing a "vegan conversion ceremony".
I just went to a vegan conversion ceremony on Thanksgiving, where we heard a lot about the joys of being vegan from the vegan host that served only meat, butter, and cheese replacements to themselves and a room full of straight up carnivore people the host has known for at least thirty years despite never once hearing even a fleeting interest from any of them in vegan food. No non-vegan food was permitted.