I haven't tried it yet but I cut out a recipe from our local newspaper.
Yellow Plum Pudding
2/3 cup sugar
2 Tbsp softened unsalted butter
3 lg eggs separated
3 Tbsp flour
1/2 cup plum puree
1 cup milk
1/8 tsp cream of tartar
350 degrees F
Cream butter and sugar. Beat in yolks one at a time.Alternately stir in flou, milk and puree.In another bowl beat whites until foamy. Add salt and cream of tartar. Beat to soft peaks. Fold egg whites into plum mixture. Pour into 1 1/2 qt souffle dish.Set dish in a larger pan with 1" of water. Bake 35-40 minutes until top is set.
6 yellow plums, halved
put in a pot with 3 Tbsp sugar and 1 tsp honey. Cover and bring to a boil.Reduce to a simmer for 3 minutes.Puree and cool completely.
We have a Yellow Egg plum with branches bending over with ripe fruit. I've been preparing plums for freezing and cooking with them all week (our variety is generally ripe in late August), with many more buckets full of fruit still waiting on the tree!
For freezing, I'm doing a very simple process of washing them, cutting in half and twisting (as you would do with a halved avocado) to separate the halves -- the pit usually comes out easily as it seems to be a freestone variety of plum. I toss the cut halves with a squeeze of fresh lemon juice to help preserve color (reduce browning) and divide the prepared plums into labeled freezer bags in typical recipe amounts like 1 cup, 2 cup or 4 cup. I could get fanatical about it and dig out my old kitchen scale to help me portion out the bags, but most recipes I'll use the frozen plums for would be pies, fruit breads, cakes or muffins, and I bake enough I'm pretty good at eyeballing amounts. Also, as I cut the fruit I toss the plum halves in my big 8 cup Pyrex pitcher, so that helps me estimate how I'll portion them out.
I've successfully used plums (fresh and frozen) in many recipes that originally call for other fruits such as berries or peaches. I've even used this variety of plum to even replace apples in the Cook's Country French Apple Cake recipe (Sept/Oct 2012). I didn't even adjust the original recipe's sugar amount because our Yellow Egg plums have a nice balance of tart and sweet, much like the Granny Smith apples this cake recipe calls for.
I plan to also use chopped plums in bran muffins, and I'll probably also use plums to replace berries in other muffin recipes. Depending on the variety of yellow plum you have and your sweet tooth, you may want to adjust any sugars in the original recipe.
Today, I took about 4 cups of the more over-ripe plums that didn't want to halve nicely for freezing and prepared them to make a sorbet. Basically, I tossed the over ripe plum halves in the food processor with sugar to taste, a squeeze of fresh lemon juice, and about a tablespoon of honey for depth of flavor and whirred it all together. I tasted it for sweetness and felt the mix didn't need any sugar or lemon adjustment, and then pressed the processed mash through a fine mesh strainer into a container that's sitting in my fridge. Tomorrow, I'll run it through my ice cream maker and should get a great sorbet. I may also try adding a couple teaspoons of instant Clear-Jel before I put it into the ice cream maker; I hear that adds a lovely smoothness to home made sorbets. We also have a good amount of fresh basil and mint in our garden, and my next batch of plum sorbet will probably have some basil or mint in it too -- I imagine I'll end up cooking the plum mash with the basil or mint (and then maybe let THAT mash sit in the fridge together overnight) before the straining step so the basil/mint can steep with the plum well enough.
Plum pie and a plum tart (with a shortbread crust) are also on the list, as we move through our tons of plums. For the pie I'll use a pâte sucrée crust, and I think I'll try Smitten Kitchen's "Great Unshrinkable Sweet Tart Shell":
For the same tart using the shortbread crust, I'll set the plum halves in a custard or frangipane base.
In the past, I've canned plums as a savory sauce made with brown sugar, black pepper, ginger and chile peppers. You can also cook pork with plums -- they are an excellent match! It's difficult for me to give you a specific recipe because it will depend on the sweetness and consistency of your plums, but it's hard to go wrong with bone-in pork shops with roasted or pan-cooked plums (add some white wine or apple juice to de-glaze your pan for the sauce).
Since I moved and gave away all my canning supplies, I won't heat-process plum jams this year, but I'll try making some plum freezer jam, which I've never done before. This link is for "red plum" freezer jam, and I don't know if the natural pectin level is significantly different with yellow plums (probably not), but this might be a good starting point for you: