Half milk, half cream

Yes, by increasing the fat content of the milk.
If, for example, you're using semi-skimmed milk, simply switch to whole milk.

And if you're already using whole milk? Well, in that case, simply stop using 100% milk and replace part of it with cream.
A simple proportion is 50% milk and 50% cream, instead of 100% milk.
With this mixture, yes, very rich, your recipe will change texture, for the better, and although its appearance won't change, the result will be much smoother.

This is what is done systematically for flans, for example, and it's a pure delight.

I'll give you a savory example: béchamel sauce, and a sweet one: far breton.
If you're used to making one of these recipes conventionally, i.e. 100% milk, try a 50-50 mix and you'll be pleasantly surprised by the results.
Note, by the way, that to mix cream and milk, it's better to use liquid cream. It's not essential, but it's easier to mix.

Of course, we're not talking about diet cooking here, it's a richer recipe with this proportion, no secret, but after all, we're not here on a diet recipe site, and you've got to treat yourself once in a while at least.

To sum up: in most recipes with milk, you can replace it with half-cream (liquid) and half-milk, for a much more delicious result.