Add huckleberries, brown sugar, and water to a saucepan. You can use white sugar if you prefer. Bring the mixture to a boil then simmer for 10 minutes over low heat.
Smash the huckleberries against the side of the pot using a wooden spoon to release the huckleberry juices. This is an optional step, but kinda fun!
Make a slurry by mixing the orange juice and cornstarch until smooth.
Add the slurry to the huckleberries and cook for an additional minute or two, until slightly thickened.
Put sugar and water in small saucepan over medium-high heat. When mixture starts bubbling, cook for 2 minutes. Add huckleberries; cook for 1 minute. Remove from heat; stir in lemon juice. Let sauce come to room temperature, stirring occasionally.