Step 1 - Make the Caramel (15-20 minutes)

1. Add the sugar, passion fruit concentrate (if using), and water to a small saucepan.
2. Cook over low to medium heat swirling the pan in a circular motion until the sugar melts and thickens into a beautiful golden-brown caramel.  This process requires your attention because the caramel will cook and darken quickly.  Be careful not to let the caramel overcook to a dark brown as it will turn bitter. Pull off the heat when it turns dark amber and begins to smell like burnt sugar. 
3. Do not stir the caramel if you can avoid it. If you use the Passion Fruit concentrate, you may need to gently whisk to keep the passion fruit homogenized as it tends to stick to the edges.
4. Carefully pour the caramel onto the bottom of the pan (wear mittens as the pan will become very hot) and turn the pan around to coat the bottom and sides as evenly as possible. Work carefully but quickly to avoid spilling because the caramel will start to harden.  If the caramel hardens and you haven’t covered the entire pan, set the pan directly over the stove burner for a few seconds at low heat. This will loosen up the caramel allowing you to work it again quickly to finish coating the pan.
5. Set the pan aside to let it cool completely. The caramel will cool to a hard surface.

Step 2 - Make the Passion Fruit Custard (2-3 minutes)

1. Preheat the oven to 350°F.
2. While the caramel is cooling, add the Condensed milk, whole milk, eggs, and passion fruit concentrate in a blender.
3. Blend on high for 10-15 seconds until everything combines well. Do not over-blend to avoid creating bubbles and a foamy mixture. The idea is to get the ingredients to just mix well and evenly. If you want to ensure the flan is the silkiest, you can pass the mixture through a fine-mesh strainer so that no small particles get into the flan.
4. Pour the mixture on top of the caramel.  I used a 9x2 inch cake pan filled to the top, but it reduced as it cooked.

Step 3 - Bake in the water bath (60-75 minutes)

1. Cover the pan with foil to keep any skin from forming and place in a larger pan where the flan can fit comfortably. Add enough hot water to cover up half of the cake pan.
2. Bake at 350 F (180 C) degrees for 1 hour and 15 minutes or until a knife inserted in the middle comes out completely clean. If the flan still looks soft in the center after the knife test and has a bit of a jiggle, it’s ok. It will firm up during refrigeration. 
3. Let the flan cool completely on a wire rack, then refrigerate covered with foil for at least 8 hours or overnight. This ensures the flan will have firmed up nicely and the flavors have intensified. It will also deliver a flan that is firm enough for unmolding.

Step 4 - Unmold the Flan

1. After the overnight rest, the next step is the unfolding.
2. Take the flan out of the fridge 20 minutes before serving time. This allows the caramel to soften.
3. Using a paring knife, pass along the edges to loosen and help it come out effortlessly.
4. Place a serving plate on top and invert quickly. Wait a few seconds until you feel (and hear) the flan come down onto the plate. Using a rubber spatula, scrape any residual caramel onto the flan, then slice, serve, and enjoy!