To ask what this means

[MrsGriff8]

I'm quite new to this so please be gentle. What does this:

mean? I've seen it as a response a few times. Thank you! xx

Have a biscuit, I think.

It's a cookie. Or, I guess you'd call it a biscuit. I've gathered that it is sort of like a sarcastic response when people are being unreasonable or they're not believable.

It means 'I think you are being deliberately goady & I don't want to engage with you'.