If you want, you can chill it a bit before eating, but this mousse won't really hold up for days. Think more like you make it right before dinner and then eat it right after, or if you are making a single serving for yourself, just chill your ramekin or cup or whatever you are going to eat it out of before you start preparing your dessert. No chilling of the finished product is necessary, especially if you are working with cold ingredients. If you've got a jar of peach purée that you, say, made right after buying peaches at the farmers market, then this takes no time at all. If you don't have one, you should probably go to the farmers market, buy some ripe peaches, and make one. Heck, make more than one and freeze the extra.
This recipe makes one reasonably-sized serving. If you want to go big, as I have lately, multiply everything times 1.5. If you are not single or have a date or a dinner party or a family, multiply times the number of people and maybe add a serving (or more) because some people want big helpings or seconds or what-have-you.
This is based on my recollection of a recipe from what claimed to be a French monastic cookbook based on the principal of seasonal eating. This recipe was pretty much the only thing I made from the book and liked, but as the cookbook cost less than $5 in the basement of the Harvard Book Store, I never felt bad about that. However, in one of my recent moves, I apparently didn't feel like I needed to keep the book either, so when I went to find the recipe a few weeks ago, I realized I must've gotten rid of the cookbook it was in. Oops!
However, as I was sure I remembered the basic ingredients, I decided to tinker till I got something I was happy with. This is it.
I know lots of fruit mousses call for gelatin. This one doesn't—not only because the original didn't, but also because I'm a vegetarian—albeit not the strictest one—but despite my occasional marshmallow, I generally don't eat gelatin because it isn't vegetarian. Besides, this is delicious without it and holds up fine so long as you eat it within a few hours of making it. Why add ingredients you don't need, after all?
Lastly, I encourage you to get crazy and use different sorts of fruit purée. I think a number of stone fruits would work. However, whatever you use should be about the consistency of peach purée and shouldn't have seeds in it. I guess you could strain out the seeds if necessary, or if the texture doesn't bother you, do what makes you happy. Also, you are likely going to have to adjust the sugar based on the sweetness of the fruit you use, so keep that in mind.
(for a single serving)
¼ cup cream
2 tsp confectioners sugar
1 tsp brandy (option, but why wouldn't you?)
3-5 tsp of peach purée (to taste)
1) Add the cream to a mixing bowl. It would be awesome if the bowl were metal and chilled, but it's not necessary. Using a mixer of whatever sort you've got, start mixing the cream on low as you add the sugar bit by bit and the brandy.
2) Once you've added the sugar and brandy, turn the mixer up to high speed until you've got whipped cream. You'll recognize it because the cream will hold its shape. Don't over mix, or you'll end up with sweetened alcoholic butter, and I'm not really sure what that's useful for. (Perhaps you could make a cake with it.)
3) Once you've got whipped cream, gently fold in the peach purée and spoon into ramekins or tea cups or whatever you plan to serve the mouse from and cover it and put it in the fridge till you are ready to eat it.