Combine milk, brunost and cream and heat to 140° F (61C), level 5 Induction or level 5 Gas cooktop.
Add the sugars and the stabilizer. Continue to heat the mixture gently to 160° F (71 C) then stir in the milk powder. Continue to heat the liquid slowly until it reaches 180° F (81 C). Cool the liquid over an ice bath before straining through a fine mesh strainer lined with cheesecloth. Churn in an ice cream maker for approximately 25 minutes then transfer to a freezer safe container and place in the freezer.
To serve, place half a nectarine cut side up, in a bowl, scoop the brunost ice cream into the nectarine and spoon a generous amount of the poaching liquid over it. Finish with a tiny pinch of Maldon sea salt.