In a medium saucepan over medium heat, combine the mixed berries and lemon juice. Cook for about 5 minutes, stirring occasionally, until the berries start to break down and release their juices.
Add the honey or maple syrup to the berry mixture, mixing well to incorporate. Taste and adjust sweetness if necessary.
Once the berries are softened, mash them gently using a fork or potato masher to your desired level of smoothness (leave some chunks for texture if preferred).
Stir in the chia seeds and a pinch of salt. Mix thoroughly.
Reduce the heat to low and let the mixture simmer for an additional 5-10 minutes, stirring often, until it thickens to your desired jam consistency.
Remove from heat and let it cool slightly before pouring into a clean jar or container.
Allow the jam to cool to room temperature, then refrigerate it for at least 1 hour to thicken further.
Notes
Serve in a small jar with a label and garnish with whole berries for aesthetic appeal.