1 Place The Blueberries, Lemon Juice, Sugar, Salt, And Cinnamon In A Medium Saucepan. Heat On Medium Heat, Stirring, Until All Of The Sugar Has Dissolved. While The Mixture Is Heating, Use A Potato Masher To Mash Up The Blueberries. When All Of The Sugar Has Dissolved, Remove From Heat And Let Cool For 10 Minutes. If You Want A Smooth Result, You Can Process The Cooled Mixture In A Food Processor, Or Skip, In Which Case You'Ll Have Pieces Of Blueberries Which Can Add Flavorful Texture To The Frozen Yogurt. 2 Stir In The Yogurt And Milk Until Completely Incorporated. Chill The Mixture In The Refrigerator For Several Hours (Or Overnight) Until Completely Cold. 3 Process The Blueberry Yogurt Mixture In Your Ice Cream Maker According To Manufacturer'S Instructions (Usually About 25 Minutes). Serve Immediately (It Will Be Soft) Or Let It Firm Up A Bit By Freezing It For Several Hours.