The dipping sauce was at least as seasonal as the potatoes. One part homemade harissa, one part Hellmann's mayonnaise. Don't scoff at the Hellmann's--more reputable Clevelanders than me base fry sauces on it (commercial grade extra heavy, ftw). For the harissa, this wasn't an authenticity contest. I roasted and peeled a few red bell peppers, tis the season after all, and food processed them with salt, toasted and ground cumin and coriander, a handful of lazily seeded fresh cayenne peppers, garlic, and a good glug of olive oil. An all hot pepper sauce would just be brutal, and at least with the roasted red peppers the heat suppressant doesn't take away from the pepper flavor like, say, beets or carrots or tomato or whatever non-chili thing that gets thrown into harissa pastes to temper the spice. The mayo-harissa mix is familiar, like the sriracha/kewpie mayo that pops up at sushi places, food trucks, and everywhere else, but the vaguely French/Tunisian condiment doesn't cause the "why the hell can't I stop eating this" effect so enjoyed with its msg laden cousin.
Harissa: just one more way to use all those hot chilies you get bombarded with on your way into fall.