Simply bury one bean in two cups of sugar - granulated, extra fine, or confectioners. Or you can slice down the side of the bean to expose the seeds, scrape them into the sugar and mix well, then bury the pod in the middle of the sugar. It takes about a week to fully flavor the sugar, and it will keep for months. When you use some of the flavored sugar, add that amount of plain sugar back to the jar for an ongoing supply.

I've made scented sugar twice, and the sugar got a little 'clumpy'. I later learned that drying the bean on a plate first might solve that problem. I was still able to use the flavored sugar... just had to smash up the lumps first.

You can also grind a dried bean together with two cups of sugar in a food processor before aging them together. Use a fine mesh sieve to remove large pieces before using.

If you use a vanilla bean for another purpose... say, to flavor the milk for a custard... don't toss it out afterward. You can recycle that bean into a batch of vanilla sugar.