Egg yolk

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Egg Yolks
How you wound up with the leftovers: You made angel food cake, macaroons, meringue or marshmallows.

Use them now: Yolks have proteins that coagulate when gently heated, giving custard, crème brûlée and ice cream their signature soft-solid feel. You only need two yolks to make mayonnaise, and if you have just one, either add it to a whole egg for richer scrambled eggs, or prepare this simple garlic aioli, which is terrific with fried foods, from potatoes to crab cakes.

Use them later: Refrigerate yolks up to four days, or freeze them in clean ice cube trays until solid and then transfer to a zip-top bag for up to three months. (Be sure to mark on the bag how many yolks it contains.)
Rice

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Rice
How you wound up with the leftovers: It turns out that your beef stir-fry didn't have quite as much sauce in need of soaking up as you'd thought.

Use it now: Fried rice is the obvious choice; sauté chopped vegetables and/or meat, add the rice, cook until heated through and bind everything with a sprinkling of soy sauce. You can also stir the cooked grains into chicken, miso or tomato soup—or steal a trick from Julia Child and use them to thicken smooth soups without adding cream (an immersion blender will puree the rice and help distribute it evenly).

Use it later: Rice holds up well in the freezer for a month or two. Thaw it in the refrigerator or, if it's in a bag, give it a few good thwacks on the counter to break it up; then microwave it for a few minutes with a bit of water.
Tomato paste

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Tomato Paste
How you wound up with the leftovers: A recipe called for a tablespoon, but you opened a whole 6-ounce can.

Use it now: Take advantage of paste's concentrated flavor and make a tomato sauce in half the time it would take with whole or chopped tomatoes: Sauté a clove of garlic in olive oil, add paste (this works best if you have most of the can left over) and a cup of water, and season with salt, pepper and a dash of oregano. Bring to a boil and then let simmer for 15 minutes.

Use it later: Dole out tablespoons of paste onto a metal baking sheet and freeze. Once the lumps are completely frozen, store them in an airtight bag for up to six months.
Chicken

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Chicken
How you wound up with the leftovers: You were too full from Sunday brunch to finish a big dinner.

Use it now: There are a million directions you can take here. Feel like Mexican? Make enchiladas: Lay a scoop of shredded chicken, cheese and any other fillings on a tortilla; roll; lay it seam side down in a baking dish; top with jarred enchilada sauce and bake. Soup? Stir pulled-apart bits of meat into broth and simmer with carrots, onions and celery. A summery sandwich? Mix the chicken with barbecue sauce and serve on a bun. Pasta? Cristina Ferrare adds it to farfalle with pesto.

Use it later: We've had mixed results with freezing chicken. You're better off refrigerating it and using the meat within three days.
Lemon peels

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Lemon Peels
How you wound up with the leftovers: You're hooked on squirting lemon juice into your seltzer.

Use them now: Citrus peels are packed with nutrients as well as a surprising amount of flavor. Grate them and sprinkle the zest on green beans or asparagus. For dessert, simmer strips in simple syrup and roll in sugar; place on cooling racks to dry, about three to five hours. (They make a lovely garnish for pound cake.)

Use them later: Wrap the zest tightly in plastic and then seal it in a zip-top bag. Again, it helps if you mark the quantity (e.g., "zest of one lemon") on the bag. To defrost, let it sit at room temperature for a few minutes and then rub the zest between your fingers to fluff it up.
Ham

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Ham
How you wound up with the leftovers: There were just too many side dishes at the party.

Use it now: Cut the meat into strips or squares and stir it into mac 'n' cheese, split pea soup, scrambled eggs or the filling of a quiche.

Use it later: Cooked ham will last three to four days in the fridge or up to two months in the freezer (although it tends to lose flavor and texture when frozen).

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