Step 1Pit and chop the nectarines. You should have about 4 cups. Place them in a bowl with the sugar and stir to combine. Set aside 30 minutes to macerate, stirring occasionally.
Step 2Lightly crush the cardamom pods with the base of a small saucepan or a rolling pin, just enough to expose the black seeds inside. Combine the cardamom, milk, cream and salt in a small saucepan and bring to a simmer over medium heat, about 5 minutes. As soon as bubbles appear around the rim and a skin forms on top, remove from heat and cover. Set aside 30 minutes to steep.
Step 3Place the fruit in a blender and strain the cream mixture over the top, discarding the spices. Puree until smooth, about 2 minutes. Bits of peel will be visible. The mixture will be slightly thinner than a milkshake. Pour it into a bowl and chill 30 minutes.
Step 4Freeze in an ice cream maker according to manufacturer's instructions. The mixture will get to the texture of soft-serve ice cream. Spoon it into a container, cover and place in the freezer for another hour to ripen. Serve immediately. If the ice cream is left overnight, it may become icy, in which case you should allow it to warm slightly outside the freezer before serving.