Tonks has seen that look before. It happened once when she called him cute, and again with a compliment about his eyes. So, as quick as it is and as quickly as he looks away, she laughs quietly and lets it pass. For now, anyway.

"Of course." The permission is given freely, half because she knows he's a masterful wizard even in his younger years and half because it's not specifically her bauble to say yes or no to. But it is their mystery, so she's happy to share it.

"It's got to have some sort of Portkey magic, and maybe a spell like Timeturners? But I thought Portkeys had to be tied to a specific spot." She sits back comfortably, theorizing as he works.