I always make these with the leftover pie crust dough when I make a pie, but sometimes they're a nice treat in and of themselves...
Step 1: Gather ingredients
For a regular pie crust, I use one cup flour and one stick butter, but for a smaller batch (such as will fit in my toaster oven) I halved the recipe. You will also need a teaspoon of sugar, ice water, and--of course--jam. Remember to preheat the oven to 350 degrees!
Step 2: Cut butter into flour
Mix 1 teaspoon sugar into 1/2 cup flour, and then add 1/2 a stick of butter. If you have a pastry cutter, great, but if not, two dinner knives work just as well. Cut the butter into small pieces, sliding the knife blades across each other to catch all the pieces. The pieces don't all have to be completely mixed into the flour, but they should be roughly the same size; you should end up with a crumbly texture.
Step 3: Add ice water
It's important to do this step slowly: better to add too little than too much, or you will end up with gooey dough. Add a few tablespoons and start whirling the mixture around with your knife. Be patient! When all the water is absorbed, add a little more.
Step 4: Mix dough
Keep slowly adding water and whirling the batter with the knife until it starts to coalesce. When it's starting to really clump together, shape it into one ball with the knife. Try not to touch the dough with your hands more than you have to.
Step 5: Chill the dough
This step is optional, but it makes the crust even flakier, so if you have time, it's worth it to stick the dough in the fridge for half an hour.