Bring a large pot of water to a rolling boil and prepare an ice water bath in a large bowl. Cut a small X into the bottom of each peach with a paring knife, then carefully lower them into the boiling water for 30 to 45 seconds.

Using a slotted spoon, transfer the peaches immediately to the ice water bath to stop the cooking process. Once cooled slightly, gently peel away the skin with your fingers or a small knife.

Place each peeled peach on a cutting board and slice it in half along the natural seam. Discard the pits and roughly chop the peach flesh into bite-sized pieces. You should have about 6 to 7 cups of chopped peaches.

Pour the chopped peaches, sugar, and lemon juice into your large pot and stir everything together gently. Let the mixture sit for about 10 minutes before turning on the heat to allow the sugar to fully penetrate the fruit.

Set the pot over medium-high heat and stir frequently until the mixture comes to a vigorous rolling boil. Skim off any foam that rises to the surface with a spoon.

Insert your candy thermometer into the pot, making sure it doesn't touch the bottom or sides. You're aiming for the mixture to reach 220 degrees Fahrenheit. At around 15 to 20 minutes into cooking, add the butter to reduce foaming.

When the thermometer reads 220 degrees Fahrenheit, remove the pot from heat and perform a plate test. Place a small amount of the hot preserves onto a cold plate and let it cool for one minute. Tilt the plate and push the jam with your finger. If it wrinkles and moves slowly, it has reached the proper consistency.

Using a ladle, carefully pour the hot preserves into clean glass jars, leaving about half an inch of headspace at the top. Place the lids on the jars and let them cool to room temperature for at least 4 to 6 hours before moving them.