Insert the Instant Pot inner pot and add 1 lb blueberries (fresh or frozen), ¼ cup water, 2 teaspoons lemon juice, and ¾ cup granulated sugar. Do not stir.

Close the lid and set the pressure valve to the Sealing position.

Select the Manual (High Pressure) setting and set the timer for 3 minutes.

When the cooking cycle ends, allow the Instant Pot to release pressure naturally (do not turn the valve). Wait until the float valve drops on its own.

Carefully open the lid, tilting it away from your face, and gently stir the cooked berry mixture.

In a small bowl, whisk 2 tablespoons cornstarch with 2 tablespoons water until smooth to make a slurry.

Select the Sauté function on the Instant Pot. Pour the cornstarch slurry into the pot and stir constantly until the mixture thickens to a jam-like consistency.

Turn off the Instant Pot and, if using, stir in 1 teaspoon vanilla extract.

Let the jam cool until it is safe to handle, then transfer it to a clean jar.

Cool the jar completely before storing the jam in the refrigerator.