Lightly spray four jello molds or small ramekins with a fine mist of the oil spray. I suggest you do this in the sink, so all the stray oil mist doesn't end up on your counter.Set the molds aside on the counter while you proceed with the following steps.
Step 2: Combine milk
In a medium bowl, combine the milk, condensed milk, vanilla extract, and instant coffee.Gently stir with a spatula to combine well (stirring vigorously will produce bubbles which we're trying to avoid).
Step 3: Mix gelatin
Add the cold water to a small bowl. Add the gelatin in a fine mist, stirring to prevent it from clumping. Once combined, cover the bowl with a clean towel, and let the mixture rest for five minutes on the counter.Once it has rested, add to the milk mixture. Sieve to remove undissolved parts (optional, if you see any clumps).
Step 4: Heating
Pour the mixture into a small saucepan, and heat over low heat, stirring constantly but gently (so you don't make bubbles) until the mixture is heated (steam starts to come out), but before it breaks the boil (before it starts bubbling). Remove from the heat and immediately pour into the ramekins or molds.
Step 5: Chill
Cover the ramekins with plastic wrap (to prevent them from forming a crust) and let them cool for 15 minutes, on the counter. Once cooled, take the ramekins to the fridge to chill for at least 4 hours, or even overnight.
Step 6: Unmold
To unmold the chilled panna cotta, slide a sharp knife all around the edge of the pudding to release the edge. Pour some warm water into a bowl, then dip the ramekins into the water bath for 5 seconds (make sure no water gets into them). This will help loosen it a bit more.Remove the ramekins from the water and pat dry on the outside to prevent water from dripping into the serving dish.
Step 7: Serving
An hour before serving, make the sauce. To make the sauce, mix dulce de leche and ice-cold water to obtain a pourable mix. Cover the sauce, and chill in the fridge.Cover the ramekin with a dessert plate and turn it upside down. If it doesn't fall immediately, shake gently to release it. Serve the panna cotta with the dulce de leche sauce.