These lovely tender pillows of homemade pasta are held together with soft tofu in place of egg, keeping them vegan.
For the gnocchi, preheat the oven to 350ºF. Prick the whole sweet potato (skin on) with a fork and bake until tender, about an hour. Cool completely before making the gnocchi.
Peel the sweet potato and puree it in a food processor with the silken tofu until smooth. Scoop the mixture into a bowl and stir in the flour and salt. Once the dough just comes together, turn it out onto a well-floured surface and bring it together. You may have to add a little more flour to achieve the proper consistency. The dough should hold together and not stick to well-floured hands. Divide the dough into pieces and roll it out into a rope about an inch in diameter. Cut gnocchi into 1-inch pieces, and place on a floured baking tray. Chill the gnocchi for 15 minutes.
To cook the gnocchi bring a large pot of salted water to a boil. Add the gnocchi and boil for 2 to 3 minutes, until they float to the top of the water. Drain well. The gnocchi can prepared up to this stage a day ahead and stored refrigerated.
For the sauce, add the oil to a large heavy-bottomed sauté pan over medium heat and add the onions and thyme. Stir the onions frequently, cooking over medium heat (or lower the heat if the begin to brown too quickly) until they are soft and a rich brown colour, about 25 minutes. If the caramelization sticks to the bottom of the pan too much, you can add a splash of white wine, balsamic vinegar or even water to loosen those flavourful bits.
While the onions are cooking, stem the kale by pulling the leaves away from the stems (discard the stems). Finely shred the kale and add this to the caramelized onions along with about 1/2 cup of water and let the kale wilt. Stir in the currants, lemon zest and lemon juice and season to taste.
To serve, warm the gnocchi in the pan with the onions and kale and then serve.