Make Caramel Syrup: Heat ½ cup (100g) white sugar and 2 tbsp (30ml) cold water in a saucepan over medium-high heat. Swirl occasionally until dark golden brown (mahogany) in color. Divide the caramel into six 177 ml ramekins. Then, allow the caramel syrup to cool.
Make Milk Mixture: Heat up 1 cup (250ml) 2% milk and 1 cup (250ml) heavy cream in a medium pot. Add ¼ cup (50g) sugar, 2 tsp (10ml) vanilla extract, and a pinch of sea salt to the hot milk, then stir until the sugar fully dissolves.
Temper Eggs: Beat 3 extra large eggs lightly in a medium bowl. Slowly bring the eggs' temperature up by pouring warm milk mixture into the eggs little by little. Continue to whisk and pour the remaining milk mixture into the eggs.
Pour Flan Mixture in Ramekins: Pour the mixture in the caramel-filled ramekins through a strainer. Then, tap ramekins against the counter to let the air bubbles rise to the surface. Remove all the bubbles on the surface with a spoon or a blowtorch. Cover each ramekin tightly with aluminum foil.
Pressure Cook Flan: Add 1 cup (250 ml) of cold water in Instant Pot. Place steamer rack in Instant Pot. Then put the covered ramekins on the rack. With Venting Knob at Venting Position, close the lid, then turn Venting Knob to Sealing Position. Pressure cook at High Pressure for 9 minutes + Natural Release. Open the lid carefully.
Chill in Fridge: Remove ramekins from Instant Pot. Set aside to cool. Refrigerate Instant Pot Flan to firm for at least 4 hours (preferably overnight).
Serve Flan: Run a knife around the ramekins and invert onto a plate. Then, serve cold!