Is biscuit countable or uncountable noun?

Well, honey, "biscuit" can be both countable and uncountable depending on the context. If you're talking about individual pieces, like "I ate three biscuits," it's countable. But if you're talking about the general concept or a mass quantity, like "I love biscuit with gravy," then it's uncountable. So, it's flexible like a gymnast, darling.