Mix sugar and water and cook in a heavy saucepan over low heat until thick dark caramel forms. Make sure it does not burn! You may need to stir it gently with a spatula to prevent it from burning on the hot spots.Pour carefully into a 5-cup baking pan and spread all over. Cool to room temperature, by then the caramel should have hardened.
2. Making the flan mixture
In the blender vase, combine eggs, condensed milk, evaporated milk, sugar, Kahlúa, instant coffee, and vanilla extract. Blend the mixture. Pour carefully into the baking pan, trying not to disturb the caramel layer.
3. Baking
Bake in a hot water bath (bain Marie) in preheated oven to 320 ºF [160ºC] for one hour or until a toothpick or thin knife inserted in the center comes out clean.
4. Serving
Remove from the oven and the water bath and cool to room temperature. Chill in the fridge. Loosen the edges of the flan with a toothpick. To unmold, place a serving plate on top of the mold (a deep-enough plate to retain the syrup) and invert. Serve still chilled.