The underlined words form a compound adjective in the given statement.
A compound adjective is formed when two or more adjectives are joined together to modify the same noun. A compound adjective can be formed using different forms of speech, which along with another part of speech function as a compound adjective. In the sentence, the words ‘mouth’ is a noun and ‘watering’ is a verb. We use a hyphen between two to make it a compound adjective that describes the Briyani, i.e. noun, to avoid confusion between the words. Thus ‘mouth-watering’ is a compound adjective, hence the statement is true.