This classic Spanish flan requires attention to detail but rewards you with an impressive dessert. The key techniques include properly caramelizing sugar without burning it, tempering eggs to prevent curdling, and using a water bath for gentle cooking. Take your time with each step, especially when making the caramel and monitoring the baking process.

1. Step 1: Proper oven temperature is crucial for the custard to set correctly without curdling.

   Preheat your oven to 325°F (165°C) and position a rack in the middle of the oven.

2. Step 2: Stirring can cause crystallization; swirling helps the sugar melt evenly.

   To make the caramel, combine 3/4 cup sugar and 1/4 cup water in a medium saucepan over medium heat. Do not stir after the sugar begins to dissolve, but gently swirl the pan occasionally.

3. Step 3: The caramel should be a rich amber color, not too dark or it will taste bitter.

   Allow the mixture to cook until it turns a deep amber color, about 8-10 minutes. Watch carefully as caramel can burn quickly.

4. Step 4: Work quickly as the caramel hardens fast. Be careful as the caramel is extremely hot.

   Immediately pour the hot caramel into a 9-inch round cake pan or flan mold, carefully tilting the pan to coat the bottom evenly. Set aside to cool and harden.

5. Step 5: Don't over-whisk the eggs as this can create air bubbles in your custard.

   In a large bowl, whisk together the 5 whole eggs and 2 egg yolks until just combined. Add the remaining 1/4 cup sugar and whisk until dissolved.

6. Step 6: Heating the dairy creates a smoother, more flavorful custard.

   In a saucepan, heat the milk and cream until it just begins to simmer (do not boil). Remove from heat.

7. Step 7: Tempering prevents the eggs from scrambling when combined with hot liquid.

   Slowly pour about 1 cup of the hot milk mixture into the egg mixture while whisking constantly to temper the eggs.

8. Step 8: Vanilla enhances the flavor while salt balances the sweetness.

   Gradually add the remaining milk mixture, whisking continuously. Stir in the vanilla extract, salt, and cinnamon (if using).

9. Step 9: Straining ensures a silky smooth texture in the final custard.

   Pour the custard mixture through a fine-mesh strainer into the caramel-lined pan to remove any egg solids or lumps.

10. Step 10: The water bath provides gentle, even heat that prevents the custard from curdling.

    Place the flan pan in a larger roasting pan and add hot water to the roasting pan until it reaches halfway up the sides of the flan pan, creating a water bath (baño maría).

11. Step 11: The flan will continue to set as it cools; don't overbake or it will become rubbery.

    Carefully transfer to the oven and bake for 50-60 minutes, or until the center is just set but still slightly jiggly.

12. Step 12: Chilling allows the flavors to develop and the texture to firm up properly.

    Remove from the water bath and let cool completely on a wire rack, then refrigerate for at least 4 hours or overnight.

13. Step 13: The caramel will flow over and around the custard, creating a beautiful sauce.

    To serve, run a thin knife around the edge of the flan to loosen it. Place a serving plate with a rim over the pan and quickly invert. Gently shake if needed to release the flan.

For the best presentation, chill the flan thoroughly before unmolding. If the caramel has hardened too much in the pan, you can place it in a shallow pan of hot water for a minute to help loosen it. Leftover flan can be stored covered in the refrigerator for up to 3 days.