Pit, skin, and slice the peaches. Place them in a large pan with enough water to prevent sticking and cook 15 to 20 minutes or until soft. Puree the peaches in a food processor and return to the saucepan, adding the brandy, lemon, sugar, and mint sprigs. Simmer over low heat, stirring frequently, 30 to 35 minutes or until the puree thickens. Remove the mint and fill clean 1/2-pint jars with peach butter to within 1/4-inch of the top. Wipe, seal, and process in a boiling water bath for 10 minutes.