Steps:

• Oven – set to 250* F – This is for heating the jars. You don’t have to heat your jars in the oven, but if you use water, you will need to dry out the jars before adding the melted butter. That’s kind of a pain, so put your jars on a baking sheet and put them in the oven set to 250*F for about 20 minutes before adding the butter.
• Go ahead and put 3-4 inches of water in your pressure canner and bring up the heat.
• Boiling butter: Put water in the pan to heat lid and rings, go ahead and bring the heat up under that as well. Put the butter in a heavy pot and melt it, bring it to a boil then reduce the heat to a simmer. Let the butter simmer for 10 minutes or so. You’re evaporating some of the moisture from the butter and getting it good and hot. Be sure to stir it and don’t allow any of the milk solids ( the little while particles) to burn and don’t let it boil over!
• Once everything is good and hot, carefully take the jars out of the oven. Place the jars right side up on a clean dish cloth and place the canning funnel in the jars one at a time and fill the jars with hot butter, leaving a 1/2" head space.
• Using a clean cloth dipped in vinegar and then squeezed out, clean off the jar rims. Place lids and rings on each jar, tighten the rings just firmly but not hard.
• Put the jars in the pressure canner that has 3-4 inches of hot water in it. I put in a couple of strategically placed clean dish cloths in case the little jars topple over. They can rattle against the sides and each other and break.
• Half-pints of butter in the canner: Put the lid on the canner and fasten it down. Allow steam to flow out of the vent for about 10 minutes. Place the weight (at 10 pounds) or gauge (11 pounds) on the vent and when it reaches the correct pressure (when the weight begins to rattle) start timing.
• Allow the pressure canner to chug along for 60 minutes for these half pints. After 60 minutes, take the canner of the heat and allow it to release its pressure naturally. You might hear the lids sealing while the jars are still in the canner, that’s okay.
• Once all the pressure is gone and you can safely open the canner, open it up and take the jars out of the canner. Place them on a clean towel to cool.
• Because this is pressure canned, and the butter is subjected to high temperatures, you may see the milk solids clump together and fall to the bottom of the jar. That’s OK! Jut give your jars a shake as they cool to combine the solids and the liquids. As the butter solidifies, the solids will be dispersed throughout the liquids and it will look like you expect butter to look.
• Check for seals after it cools. Store canned butter in a dark cool, dark place, (a cardboard box works great). If you want the butter to be firm, then refrigerate a jar before you open it. Whatever you don't use, just store in the fridge until you need it again.