Roast sweet potatoes in a preheated oven (425 degrees F) for 45-60 minutes, or until a cooked through. Cool for a minimum of 15 minutes; overnight in the fridge also works.

Start a pot of salted water to boil. Peel potatoes and use a potato ricer to rice potatoes into a bowl.

In a separate bowl, mix flours and salt to combine. Add sweet potato to flour and knead with your hands until all flour is incorporated.

Dust 1 tablespoon (additional) arrowroot powder to your work surface and place ball of dough on the flour. Break into 3-4 smaller balls, and roll each out into rope-like pieces. Cut the "ropes" into 1" pieces, dusting with additional arrowroot flour if your surface is getting sticky.

Adjust boiling water to a medium boil and pour half of the gnocchi in. Wait until they begin to float to the top, then let cook for a minute or two. Remove with a slotted spoon and lay on a cutting board (or plate). Place cutting board in refrigerator, and cook the other half of the gnocchi the same way.

To make the sauce: Cook the butter over medium-high heat in a saute pan.

Add the sage leaves to the melted butter and cook until butter begins to turn brown; remove from heat immediately.

Plate the gnocchi and pour sage brown butter sauce on top. Serve while warm.