The plural forms of material nouns such as "butter"
"How many grammes of butter is in the cake?" Is this wrong? The answer says "are in the cake"
Grammes is the subject, not butter. (Butter is modifying grammes.) So, it's "grammes are" not "butter is." Native speaker.
In this sentence, the subject is not "butter," but "grammes." That's why the verb is "are."
Thank you, for your comments. I tried to convince myself thinking like that but it still doesn't make sense to me. I'll wait for another comment by a native speaker of English.
I am another native speaker of English. It would be "How many grams are there?" You wouldn't say "How many grams is there?"
If you have a noun (in this case "butter") which follows a preposition, you know that the noun cannot be the subject of the sentence, so the verb does not apply to it.
The previous posters were correct in their comments, and I would like to point out that many non-native speakers of English have a better knowledge of grammar rules in English than we native speakers.
For what it's worth, I am a native speaker. So is RJ_G, who just commented.
Another native chiming in; the "are" does indeed refer to the grams, not the butter. Butter is (usually?) an uncountable noun, we talk about butter, not about butters! But if it is being measured, then it will be X grams (or ounces or...) of butter, and it is the unit of measurement (grams, spoonfuls, etc) that will govern whether the verb is singular or plural.
Same applies to things like sugar, salt, water... we say X amount OF something, and the unit of measurement is what governs the verb.
Regarding your parenthetical (usually?), I think it could be pluralized in specific contexts like "The store had a wide selection of European butters" or "This cookbook has recipes for different fruit butters"