ShareSaveAdd as preferred on GoogleMark SavageMusic correspondentBBCI'll find a better way / To explain this to you... Under one condition, though / It's unconditional," he sings.
"It's kind of a mournful song," he says, choosing his words carefully. "You're expressing how... how deeply sorry you are for... something.
"When you write a song like that, and you listen to it back, you kind of understand how you feel in yourself. And that makes it easier to use those words outside of the song, right?"
Grohl won't be drawn on the specific circumstances behind the song. "I can tell you're baiting the hook," he says (amiably) when I broach the subject, before offering a more general observation.
"You know, this band was born out of the pain of losing Kurt [Cobain] and Nirvana, so we've always relied on music to help us through difficult times - and it has certainly done that in my life in the last year and a half.
"At the same time," he continues, "it's one thing to send the world all these lyrics, and it's another to really delve into deeply personal things.
"So there are some things that I reserve for my personal conversations."
As he acknowledges, the Foo Fighters' story was forged in tragedy, and Your Favourite Toy is the band's second release since the death of their beloved drummer Taylor Hawkins in 2022.
That loss was addressed on 2023's mournful, contemplative album But Here We Are. Today, the band have a new drummer, Ilan Rubin, but they're still grieving.
"We are a different band," says Mendel. "Taylor was such an energetic presence, he just brought himself so much."
After Hawkins was found dead in his hotel room, hours before a concert, Mendel thought the band were finished.
"I was like, 'Can we still do this without Taylor?', and I'm sure everyone else felt that, too.
"But one thing that I've come to realise - this sounds a little hokey, but it's true - is that Taylor is with us. His wife is on the road with us right now. We're still very close to the Hawkins family. We talk about him every day."
Grohl adds: "Continuing as a band was not easy. We were like best friends and brothers - so it was really complicated and felt really strange for a little while.
"When you go through any sort of trauma or loss, you have to do everything all over again. So the next day, that's the first cup of coffee since it happened. Then it's the first song we've written since it happened.
"But whenever we go through something really difficult, we go through it together, with our families and our kids and our wives. We really rally.
"And if you're surrounded by people that you know you can really rely on, that's the key."
One of those people was Sir Paul McCartney, who invited Grohl to join him on stage Glastonbury in June 2022.
It was the star's first public appearance since Hawkins' death, and the gesture meant the world – even if he almost missed the show after his flights were cancelled.
"I walked backstage 20 minutes before we were supposed to go on, so the whole thing was kind of a blur, but it meant a lot, for sure.
"He and his family were always so sweet and supportive and welcoming."
So has he thought about returning the favour and asking Sir Paul along when Foo Fighters play Liverpool's Anfield Stadium this summer?
"Someone asked that this week," he says. "And then, of course, all the headlines said, 'Dave Grohl has asked Paul to play in Liverpool'.
"I have not asked. I only texted and said, 'Hey, we're playing in your home town'. And he goes, 'You'll love it.'"
If the former Beatle does join them backstage, he may find that the encroachment of age has altered their pre-show rituals.
In the past, they'd slam tequila shots before walking into the spotlights. These days, "we do nap sometimes", Grohl admits; while Mendel confesses that the band can often be found building Lego sets in the dressing room.
"Not very rock 'n' roll, is it?" laughs Grohl, who has constructed the Eiffel Tower, the White House "and several Harry Potter castles" out of plastic bricks.
There is "something sort of meditative" about the process, he says. "You can just turn your brain off and follow the instructions.
"It's like Ikea furniture. I've built a lot of Ikea furniture in my time and you feel so proud."
However, cocktails do start flowing an hour before show time.
"Then the laughter gets a little louder, and the music gets a little louder and, just before we walk on stage, we're having the best time of our lives, so we hit the stage with a smile.
"It sounds so ridiculous, but to me, that's the most important part. There's no faking it in this band. You get on stage and you have those few hours to do it - and you've got to do it for real."
