I’m not an empty nester but due to food allergies my wife and I eat different things. I find a good kitchen scale to be a hard requirement. Just take your recipe and scale it down. For pasta, I weigh the entire box, divide by four, weigh out and cook that fourth.

1. Freeze leftovers. If food is too much, put 1-2 meals in a freezer-ready container, put it away. Eat it a few weeks/months later when you’re too lazy to cook.

2. Measure ingredient amounts. Usually, I don’t bother, but if I don’t want leftovers, it’s necessary.

I don’t really consider food I cook to be leftovers. It’s just prepping ahead. That means I don’t have to cook tomorrow.

Some dishes freeze well, so those leftovers can be turned into future meal prep. I liked freezing my chili in silicone muffin tins, then one or two thawed chili pucks was a perfect last-minute meal when I didn’t feel like cooking.

I had to work on this issue. I used to massively overcook. My house was always the place people just showed up. I had two kids, friends, family, so I was constantly ready to feed an army. Now one is out of the house, the other isn’t home most of the time and husband works evenings. We don’t have company like we used to before Covid, so unannounced guests happen rarely.

I have to be conscious at all times about what I’m cooking. First I had to admit that my perception of how much food I needed was just wrong and could not be trusted. I started using recipes - even for things I know how to make- purely to reference serving sizes. And when all else failed, however much I felt I needed to make, I’d just make half of that

It took some practice but now I make reasonable sized meals and have few leftovers.

Buy and make smaller portions? Start trading around leftovers with neighbors and friends?

I’m not an empty nester just live alone but I just make enough for 2/3 meals so I can have days off from cooking. If a recipe serves like 6/8 I cut all the ingredient measurements in half. I don’t really do box mac and cheese as a side because it’s too much for just me. I suppose you could try making half a box at a time but I don’t know how well the powder would keep.

Smaller pans may help because it forces you to cook smaller amounts.
Another possible thing to try is to cook 1 pot dishes

Lunch the next day. I fail to see the problem. It’s a massive time saver. You need to join a meal prep community to fully appreciate it! It’s a time and money saver

That’s what the freezer is for. I still cook for four, because most ingredients are packed in a way that favors making a meal for four people, but that just means there are two helpings that can get into the freezer for another day.

Find an elderly friend nearby you can share with?

I freeze the leftovers, and don’t necessarily eat your same leftovers multiple days in a row. So if I cook three days in a row, that’s probably enough leftovers to rotate between three for a total of nearly two weeks.

I mostly cook stews and sauces, and cook fresh rice or pasta to go with it, because these foods tend to freeze really well.

Just start feeding the neighbour teenager. Bottomless pit just waiting for all your spare cooking.

Or, halve the recipes. If you don’t cook enough you can always top up with a snack.

Like many people have said: freezer.

We have a box of quart-sizes freezer zip bags. Whenever you make food, immediately separate half of what you made and freeze it. You can always thaw it later when you don’t have time or energy to prepare food.

Dairy tends not to freeze well. Most other foods do. You can freeze pasta, rice, and bread easily, so make a bunch to mix in to future dishes, and if you can’t get through a full loaf of bread before it spoils, freeze half the loaf as soon as you bring it home.

There are a lot of meal prep tips websites, and it sounds like you are inadvertently meal-prepping. See what tips they have for storing food.

I’ve found smaller portions to be a waste of time. It takes just as long, but you don’t get as much out of it.

Yes, the freezer is one key. I’d actually like to get a chest freezer too.

Another trick is re-use. I’ll cook a steak, save half for stir fry, ramen, nachos, sandwich, etc. A chicken gets legs and thighs used for dinner, breasts for chicken salad, and bones and bits for soup.

Cans are also great. They serve a dual purpose of emergency-kit food and (since they eventually need to be rotated) super-lazy meals. I generally keep, maybe 20 various cans of chilli, soup, beans, spam, tuna, crab, tomatoes, etc. and make a point of using a couple every month, just to keep things from getting too old.

The real difficulty I run into is making good salads. It takes just as much time to make salad for six as for two. I often just settle for the bagged stuff, but it feels wasteful and uninspired.