Step 1: Crafting the Liquid Gold Caramel

1. Prepare Your Pan: Lightly grease a 12-cup muffin tin. This will ensure the muffins release easily once baked and cooled. You can also use muffin liners if preferred, though the caramel might stick slightly to paper liners.
2. Combine Sugar and Water: In a medium saucepan, combine the 1 cup of granulated sugar and ¼ cup of water. Stir gently to ensure the sugar is moistened.
3. Caramelize the Sugar: Place the saucepan over medium heat. Now, resist the urge to stir! Stirring can cause crystallization. Let the mixture heat undisturbed. As it heats, the sugar will dissolve, then begin to bubble and turn a light golden color.
4. Watch Closely and Swirl: Once the sugar starts to caramelize, watch it very carefully. It will transition from golden to amber quite quickly. You can gently swirl the pan occasionally to ensure even caramelization.
5. Achieve Amber Perfection: Cook until the caramel reaches a rich amber color. Be mindful not to let it get too dark brown, as it can become bitter. The color should resemble dark honey.
6. Quickly Pour into Muffin Tin: Immediately and carefully pour a spoonful of the hot caramel into the bottom of each muffin cup in the prepared tin. Work quickly as the caramel will start to harden as it cools. Aim for an even layer in each cup.
7. Let Caramel Harden: Allow the caramel to cool and harden in the muffin tin while you prepare the flan and muffin batter. This will create a stable base for the flan and muffin layers.

Step 2: Preparing the Silky Smooth Flan Filling

1. Preheat Oven and Prepare Water Bath: Preheat your oven to 350°F (175°C). Prepare a water bath by placing a large roasting pan or baking dish on the lower rack of your oven. Have a kettle of hot water ready.
2. Combine Flan Ingredients: In a blender or food processor, combine the sweetened condensed milk, evaporated milk, eggs, and vanilla extract.
3. Blend Until Smooth: Blend on low speed until all ingredients are thoroughly combined and the mixture is smooth and lump-free. Avoid over-blending, which can incorporate too much air.
4. Gently Pour Flan over Caramel: Carefully and slowly pour the flan mixture over the hardened caramel in each muffin cup. Pouring slowly helps prevent the caramel from splashing and ensures an even layer of flan.

Step 3: Mixing the Tender Muffin Batter

1. Whisk Dry Ingredients: In a large bowl, whisk together the all-purpose flour, granulated sugar, baking powder, baking soda, and salt. Whisking ensures the dry ingredients are evenly distributed and lump-free.
2. Combine Wet Ingredients: In a separate bowl, whisk together the melted and cooled butter, buttermilk, eggs, and vanilla extract until well combined.
3. Combine Wet and Dry: Pour the wet ingredients into the dry ingredients. Using a spatula or wooden spoon, gently fold the wet and dry ingredients together until just combined. Be careful not to overmix. Overmixing develops gluten, which can result in tough muffins. A few streaks of flour are okay at this stage.
4. Spoon Muffin Batter over Flan: Gently spoon the muffin batter over the flan layer in each muffin cup. Fill each cup about ¾ full. The muffin batter will be lighter than the flan and will sit on top.

Step 4: Baking and Setting the Magic

1. Pour Hot Water into Water Bath: Carefully pour hot water into the prepared roasting pan or baking dish in your oven until it reaches about halfway up the sides of the muffin tin. This water bath creates a humid environment that is crucial for baking flan and ensures even cooking and a creamy texture.
2. Bake to Perfection: Carefully place the muffin tin into the water bath in the preheated oven. Bake for 30-35 minutes, or until a toothpick inserted into the muffin portion comes out clean. The flan will be set but still slightly jiggly.
3. Cool in Water Bath: Once baked, carefully remove the muffin tin from the oven and let it cool in the water bath for about 15-20 minutes. This gradual cooling helps prevent the flan from cracking.
4. Refrigerate to Chill: Remove the muffin tin from the water bath and let it cool completely at room temperature. Then, refrigerate for at least 2 hours, or preferably overnight, to allow the flan to fully set and the flavors to meld.

Step 5: Unmolding and Serving

1. Loosen Edges: Before unmolding, gently run a thin knife or spatula around the edges of each muffin cup to loosen them.
2. Invert onto Plates: Place a serving plate over each muffin cup and carefully invert the muffin. The caramel should now be on top, drizzling down the sides.
3. Serve and Enjoy: Serve chilled or at room temperature. Garnish as desired (see “How to Serve” section for ideas) and prepare for rave reviews!