"D'ól sé bolgam maith den bhlathach. B'aoibheann leis a ghéire agus a fhuaire a bhí."

I don't understand the construction of the second sentence. Could someone break it down for me?

Go raibh míle maith agaibh

Oscar

*sentence from 'An Litir'

He drank a good mouthful of buttermilk. He loved how sour and cold it was.

B'aoibhinn leis = "was delightful with him" -> he loved, he adored,
a ghéire a bhí (sí)* = "its sourness that was [she]" -> how sour it was (it = buttermilk)
a fhuaire a bhí (sí)* = "its coldness that was [she]" -> how cold it was

géire, fuaire are abstract nouns (of degree), just like méad, laghad or feabhas.
Together with the possessive pronoun a (his / its) they mean "how ..."
A relative clause follows.

e.g. a fheabhas atá sé = how good he is



* (sí) - I would think a subject is necessary here. So sí is missing in the quote from the book.

Thanks, Labhrás. This is enlightening