Christine Burns Rudalevige rolls out sweet potato gnocchi. Shawn Patrick Ouellette/Staff Photographer

I have a memory of making gnocchi with my cousins on a rainy day when I was very young. Our Nonna, who made gnocchi only on rainy days because she said the humidity helped the process, mixed the dough according to feel. The ingredients were standard, a combination of boiled potatoes pushed through a ricer, white flour and egg yolks. She’d learned from her mother to know when the dough felt just right: supple but not sticky, the balance that’s required for gnocchi to hold together while being cooked in boiling salted water.

Standing around her laminate-topped kitchen table, our many little hands gently rolled pieces of the dumpling dough along fork tines. That part of the process, tedious for one but fun for many, makes the grooves in the dumplings, which ensure the sauce will eventually stick.

This scene was set in the time before one could buy gnocchi in the frozen food aisle. And it wasn’t repeated once the commercial ones did hit the market. Nonna was perfectly OK with eating frozen gnocchi. Her day job was cooking at a local nursing home, so she appreciated convenience foods. She considered the frozen variety to be a decent approximation of homemade potato gnocchi, without all the mess.

I’m guessing, though, she’d have a few choice words – she generally tossed out gentle criticism in Italian – if she were here to hear me say that one can make pretty good gnocchi from leftover mashed potatoes. Maybe she’d say “sempliciotta.”  That’s someone who makes rookie mistakes.

She wouldn’t resort to this name-calling because she was dismayed by my mucking with an age-old culinary tradition but because she hated the very idea of leftovers. Not only did she dislike eating the same thing twice in close succession, her waste-not-want-not philosophy hinged on never making too much food in the first place. My rookie mistake, in her eyes, would be misjudging how many mashed potatoes I needed.

Cooking only what you need is a perfectly reasonable green eating tenet. But what if, despite perfectly executing the holiday meal, you still find yourself with a cup or so of mashed white or sweet potatoes in the fridge because one of your guest passed on them in order to eat two kinds of pie? A cup is not enough to make a meal – unless, of course, you add some flour and an egg and turn it into gnocchi.

The general ratio for mashed potato gnocchi is one cup of mashed potatoes to one cup of all-purpose flour and one egg. No salt is needed as you already seasoned the potatoes the first time you served them. Just as Nonnas everywhere adjust for the water in the potatoes and for the humidity in the air, you too must adjust for what you’ve already put in your potatoes. I put butter and mascarpone cheese (for white potatoes) or crème fraiche (for sweet potatoes) in mine. They are more fluffy than spreadable because I don’t add any additional liquid. But if your mashed potatoes include milk or broth, you might have to bump up the flour to 1 ¼ cups or use just the egg yolk (rather than a whole egg) to get the gnocchi dough just right.

Freshly made (but uncooked) gnocchi on baking sheets made from mashed sweet potatoes. Shawn Patrick Ouellette/Staff Photographer

The dough should hold together and still be a little moist but not sticky. The texture should feel like pizza dough. If you’ve never handled raw pizza dough, squeeze your earlobe gently between your thumb and index finger and you’ll get the general idea.

Start with cold mashed potatoes. Add the egg first, followed by the flour. Use a fork to mix this combination into a shaggy dough. Dump the dough out onto a lightly floured surface and work it gently until it comes together in a smooth ball, but just.  Overworking will make the gnocchi tough, and you want these babies tender.

Divide the dough into three pieces, roll each piece into a rope, about 15 inches long and 1-inch in diameter. Cut each rope into about 20 (3/4-inch) pieces. Pick up one piece of dough and use your thumb to gently roll it over the gnocchi board (called a rigagnocchi) or the back of the fork to create grooves in the dough. Repeat to roll all the gnocchi. As you roll them, put the formed gnocchi onto a baking sheet sprinkled with semolina, placing them in a single layer and making sure they don’t touch.

Unless you freeze them, gnocchi are best cooked within three hours of being made. To do that, put the whole baking sheet in the freezer and, once they are individually frozen, transfer the gnocchi to a container, where they will keep for up to three months. Pull them out of the freezer, like my Nonna did, when you need a good meal in 10 minutes flat.

Sweet Potato Gnocchi with Smokey Brown Butter and Sage finished with shaved pecorino cheese. Shawn Patrick Ouellette/Staff Photographer

Mashed Sweet Potato Gnocchi with Smokey Brown Butter Sage Sauce

Casco Bay Creamery makes Applewood Smoked Butter, which you can buy in specialty shops like Kennebec Meat Co. in Bath and the Crooked Face Creamery shop in Skowhegan. If you can’t find it, use plain butter, and add a pinch of smoked paprika.

Serves 4

Semolina
1 cup mashed sweet potato
1 egg
1 to 1 ¼ cups all-purpose flour, more for rolling
Salt
4 tablespoons Applewood Smoked Butter
1/4 cup torn sage leaves
Grated pecorino cheese

Lightly sprinkle semolina all over a baking sheet.

Combine sweet potatoes and egg in a bowl. Add 1 cup of flour. Use a fork to mix into a shaggy dough. If the dough is too wet to be shaggy, add the remaining flour. Dump the dough onto a lightly floured surface and work it gently until it comes together in a smooth ball.

Divide the dough into three pieces. Roll each piece into a rope, about 15 inches long and 1-inch in diameter.  Cut each rope into 20, 3/4-inch pieces. Pick up one piece and use your thumb to gently roll it over a gnocchi board or the back of the fork to create grooves. Place the formed gnocchi on the prepared baking tray. Repeat to roll all the gnocchi.

Place a large pot of salted water over high heat. Cover and bring to a rolling boil.

In the meantime, melt the butter in a large skillet over medium high heat. Once it starts to foam, add the sage leaves. Give them a minute to sizzle.  Then turn off the heat.

Add half of the gnocchi to the boiling water. They will sink at first, and after about 2 minutes rise to the top. Using a slotted spoon, convey the cooked gnocchi to the pan with the butter sauce. Bring the water back to a boil. Cook the remaining gnocchi, and add them to the pan with the butter sauce.

Turn the heat under the skillet to high. Swirl the pan so that the gnocchi are covered in sauce. Let the gnocchi sizzle in the sauce for 2 minutes. Transfer to a serving bowl.  Sprinkle with pecorino cheese and serve hot.

Local foods advocate Christine Burns Rudalevige is the editor of Edible Maine magazine and the author of “Green Plate Special,” both a column about eating sustainably in the Portland Press Herald and the name of her 2017 cookbook. She can be contacted at: cburns1227@gmail.com