Heat the strawberries, pure maple syrup, and lemon juice in a saucepan over medium-high heat, covered. Allow the mixture to come to a full boil then reduce the heat to a controlled boil and continue cooking until strawberries have softened, about 10 to 15 minutes. Mash the strawberries using a fork or a potato masher, until your desired consistency is reached (I like to leave mine fairly chunky).: The first aromas you notice will be bright and fruity, the saucepan starting to steam gently under the lid, signaling that juices are being released. Listen for a soft simmer and watch for bubbles collecting at the edges, which shows the mixture is coming together. I like to use a heavy bottom saucepan so heat distributes evenly, preventing hot spots that can scorch the fruit. A common mistake is using too high heat, which can cause the fruit to burn rather than simmer; keep the flame controlled so the sugars melt into the fruit slowly.
Add the ground cinnamon, sea salt, and chia seeds and stir well. Continue cooking, uncovered, until the mixture thickens, about 8 minutes. Remove from the heat and allow the jam to cool for 10 minutes. Add the pure vanilla extract and stir well.: As the mixture reaches a vigorous boil, the scent becomes intensely strawberry and sweet, and the bubbling will be steady but not violent. Reducing to a controlled boil ensures the fruit breaks down without sticking. You'll see the berries collapse and turn syrupy, with their color deepening to a glossy red. If you rush this stage you might end up with undercooked, tart pieces, so be patient and stir occasionally to prevent sticking to the pan.
Transfer the jam to a bowl and refrigerate until chilled (note: you can also put the bowl in the freezer for about 40 minutes and stir periodically to speed up the process). Once cool, transfer the jam to a sanitized jar and seal it well. Jam keeps in the refrigerator for up to 2 weeks.: When you start mashing, the sound is soft and pulpy, and the texture goes from whole fruit to a blend of chunks and syrup. The mashed pieces release more juice, which helps the jam thicken evenly. Leave it chunkier if you prefer visible fruit, or mash more thoroughly for a smoother spread. A pitfall here is overmashing which can make the jam too uniform and less interesting texturally, so stop when it feels right to you.
Add the ground cinnamon, sea salt, and chia seeds and stir well.: At this point the aroma changes subtly as the warm note of ground cinnamon rises and the sea salt sharpens the fruit. Stirring in the chia seeds distributes them so they can hydrate evenly, and the mixture will begin to look thicker and slightly grainy as the seeds absorb liquid. If the seeds clump, stir more vigorously to separate them. A common error is adding the chia too early; they can swell excessively if left to sit too long while still cold.
Continue cooking, uncovered, until the mixture thickens, about 8 minutes.: Cooking uncovered allows steam to escape and the jam to concentrate, producing a deeper smell and glossy sheen. Watch for the mixture to reduce and for bubbles to become larger and slower, which indicates thickening. The surface will look syrupy and coat the spoon. Avoid walking away during this time because the jam can quickly go from perfect to over reduced and sticky if it reduces too much.
Remove from the heat and allow the jam to cool for 10 minutes.: Off the stove the jam will relax and the intense boiling scent softens into a warm, comforting aroma. Cooling allows the texture to stabilize as the chia seeds finish absorbing liquid. Resist the urge to taste immediately if it is very hot, and avoid sealing while still warm as condensation can form in the jar and affect shelf life.
Add the pure vanilla extract and stir well.: Adding pure vanilla extract off the heat preserves its delicate fragrance, which melds with the fruity notes into a rounded finish. Stirring disperses the extract evenly so every spoonful benefits from the slight sweet perfume. A mistake is heating vanilla directly which can cause the flavor to fade, so always add it at the end.
Transfer the jam to a bowl and refrigerate until chilled: The jam will give off a heady, sweet steam as you transfer it, and chilling firms the set as the chia seeds complete their swelling. I sometimes put the bowl in the freezer for 40 minutes, stirring periodically to cool faster and test consistency. Avoid overcrowding the fridge with warm containers because that can raise internal temperatures and affect other foods.
Once cool, transfer the jam to a sanitized jar and seal it well.: When the jar is sealed, the jam's scent is preserved and the surface will look glossy and even. Sanitizing prevents spoilage and helps the jam keep well; I like to pour while warm into preheated jars so lids seal properly. A common oversight is skipping sanitation which can shorten the jam's refrigerated life.
Jam keeps in the refrigerator for up to 2 weeks.: Stored cold, the jam remains vibrant and spreads easily. During storage the texture may continue to firm slightly as the chia seeds fully hydrate. Always use a clean spoon to avoid introducing contaminants, and check for off smells or mold before using if stored for longer than suggested.