The sentence you wrote is almost correct! Here's the sentence:
Chocolate or vanilla, every ice cream starts with milk from cows.
It's a bit better to say:
Chocolate or vanilla, every ice cream starts with milk from cows.
The sentence is understandable, but to make it clearer, you can write:
Every ice cream, whether chocolate or vanilla, starts with milk from cows.
Or simply:
Every ice cream, like chocolate or vanilla, starts with milk from cows.
This way, the sentence connects the flavors (chocolate or vanilla) to the ice cream more clearly.
Good job using simple words to explain ice cream ingredients!