In a blender, combine the milk, keto condensed milk, avocado, ice, coffee, and salt & blend on high speed until smooth for about 30 seconds to 1 minute until mixture is smooth.
If the milkshake is thicker than you'd like, blend in more milk to thin it out slightly.
Melt the dark chocolate in a microwave for 30 sec-1 min, stir until smooth then drizzle along the inside of the serving glasses.
Then divide the shake evenly between the glasses, and add the whipped double cream on top if desired.
Best served immediately