How to Make It
Preheat the oven to 425°. Spread the pine nuts on a rimmed baking sheet and toast until golden brown, about 3 minutes. Transfer the nuts to a work surface and let cool, then chop and transfer to a small bowl. Stir in the mint, lemon zest and juice and ¼ cup of the olive oil. Season the pesto with salt.
On a large rimmed baking sheet, spread the sweet potatoes in a single layer. Bake until tender, about 20 minutes. Transfer to a food processor and let cool, then pulse until smooth. Scrape the pureed sweet potatoes into a large bowl and stir in the flour, cornstarch and 1 teaspoon of salt.
Lightly dust a rimmed baking sheet with flour. On a lightly floured work surface, cut the dough into 8 pieces and roll each piece into a 1/2-inch-thick rope, about 15 inches long. Using a knife, cut the ropes into 1-inch pieces. Roll each piece against the tines of a fork to make ridges and transfer to the prepared baking sheet.
In a large pot of salted boiling water, cook the gnocchi until they rise to the surface, then cook for 1 minute longer. Drain well and transfer to a serving bowl. Toss with the remaining 2 tablespoons of olive oil, then spoon the pesto on top. Sprinkle with thyme leaves and more salt; serve.
Gluten-free flour can be found at Whole Foods or on amazon.com.