Marinate the peaches: In small bowl, combine chopped up peaches with 1/2 cup sugar and lemon juice. Let sit for about an hour to get sweet and juicy.
Make the ice cream base: In saucepan, add egg yolks and 3/4 C. sugar and briefly whisk together. Add heavy cream and milk, whisk to combine. Heat mixture over medium heat while continuing to stir until mixture thickens and coats the back of a wooden spoon. Swipe your finger across the mixture on the back of the spoon and if the edges stay put, it’s ready. If you have a candy thermometer cook to 170º
Strain mixture into bowl and set in ice bath for about 30 minutes to cool down (stir occasionally). Add the peaches to the base and store in refrigerator for a few hours or overnight to thoroughly chill prior to churning the ice cream. You can blend the peaches first if you want a smooth ice cream or leave them a bit chunky if you want some peach chunks in your finished ice cream. The peach chunks will freeze harder than the ice cream. You can also save some of the peaches and swirl them in after churning.
Place churned ice cream into freezer container. If you’ve saved some peaches to swirl in, just layer half of the churned ice cream in the container, layer the reserved peaches, top with remaining churned ice cream and swirl the peach mixture through the ice cream with a knife or spoon. Cover and freeze until firm.
If you’re using a Ninja Creami, pour the ice cream mixture once its cooled into pint containers and freeze overnight. Spin on ice cream setting. Freeze to firm up as desired.