Start by placing clean jars, lids, and rings into a large pot of water and bring to a boil for 10 minutes, then reduce heat to a simmer to keep them sterilized while you prepare the jam. Meanwhile, peel and dice your peaches into 1/2-inch pieces—I find that blanching peaches in boiling water for 30 seconds first makes peeling much easier. This parallel timing means your jars will be ready exactly when your jam is finished cooking.

In a large heavy-bottomed pot, combine the diced peaches with the pectin, butter, and pumpkin spice. Mix well to distribute the pectin evenly throughout the fruit—this prevents clumping when the mixture heats up. Bring the mixture to a rolling boil over high heat and maintain that boil for about 20 minutes, stirring occasionally. The peaches will gradually soften and release their juices, creating a syrupy base.

After 20 minutes of boiling, the peaches should be very soft. Using an immersion blender or potato masher, break down the fruit to your preferred consistency—I prefer leaving some small chunks for texture rather than making it completely smooth, which gives the jam a more rustic, cobbler-like feel. This step typically takes just 2-3 minutes.

Add the sugar, lemon juice, and vanilla extract to the mashed peach mixture and stir thoroughly to combine. Bring back to a boil and maintain a hard rolling boil for exactly 1 minute—this activates the pectin and helps the jam reach proper setting consistency. Remove from heat immediately and skim off any foam from the surface with a spoon.

Carefully remove each jar from the simmering water using tongs and empty out any remaining water. Working quickly while the jam is still hot, ladle it into the sterilized jars, leaving exactly 1/4 inch of headspace from the rim. Use a clean knife or bubble remover to run around the inside of each jar to release any trapped air bubbles, then wipe the jar rims clean with a damp cloth to ensure proper sealing.

Place the lids on the jars and screw the rings on finger-tight—not too tight, as steam needs to escape during processing. Return the filled jars to the pot of boiling water, ensuring they're completely covered by at least 1 inch of water, and boil for 10 minutes. This water bath processing seals the jars and ensures shelf stability.

Carefully remove the jars from the boiling water using tongs and place them on a clean kitchen towel or cooling rack. Allow them to cool completely at room temperature for at least 12 hours without moving them—you'll hear a satisfying 'pop' as each jar seals. Once cooled, check that the lids are concave (slightly dented inward), indicating a proper seal. Store in a cool, dark place for up to one year.