1) Preheat the oven to 210°C/gas mark 7.
2) Pierce the sweet potatoes with a fork. Bake them until tender and fully cooked, between 40 to 55 minutes depending on size. Cool slightly.
3) Cut sweet potatoes in half and scoop the flesh into a large bowl. Mash the sweet potatoes, add the ricotta cheese, salt, cinnamon and pepper and blend until well mixed. Add the flour, 70g at a time until a soft dough forms.
4) Lightly flour a work surface and place the dough in a ball on the work surface. Divide the dough into six equal balls. Roll out each ball into a 2 1/2 cm-wide rope. Cut each rope into 2 1/2 cm pieces. Roll the gnocchi over the tines of a fork. Transfer the formed gnocchi to a large baking sheet. Continue with the remaining gnocchi.
5) Meanwhile, bring a large pot of salted water to a boil over high heat. Add the gnocchi in three batches and cook until tender but still firm to the bite, stirring occasionally, about 5 to 6 minutes. Drain the gnocchi using a slotted spoon onto a baking sheet. Tent with foil to keep warm and continue with the remaining gnocchi.
Brown butter sauce:
1) While the gnocchi are cooking, melt the butter in a large saute pan over medium heat. When the butter has melted, add the sage leaves. Continue to cook, swirling the butter occasionally, until the foam subsides and the milk solids begin to brown.
2) Remove the pan from the heat. Stir in the cinnamon, maple syrup, salt and pepper. Careful, the mixture will bubble up. Gently stir the mixture. When the bubbles subside, toss the cooked gnocchi in the brown butter.
Transfer the gnocchi to a serving dish and serve immediately.