Preheat the oven to 280 degrees F (140 C).
Prepare a tray with 6 six ounce ramekins.
Add 3 tablespoons of water to a pot with a lid and then add the sugar into the middle of the pot. Cover with a lid and bring the mixture to a boil. Continue to boil with the lid on until the sugar has completely melted.
Once the sugar has melted remove the lid and and start measuring the temperature. You can stir it at this point if you need to.
When the caramel reaches a medium brown color (350 degrees F), remove the pot from the heat and quickly and carefully pour 2 tablespoons of room temperature water into it, whisking to combine. Be very careful as the hot caramel will sputter.
Divide the caramel between the ramekins.
Boil some water
To prepare the custard for the Panna Cotta, put the cream, sugar, and vanilla in a pot and heat, stirring until the sugar has fully dissolved (don't let the mixture boil). Remove the pot from the heat and let it cool to lukewarm. You can use an ice bath to speed this up.
While you're waiting for the cream to cool, measure out the egg whites into a tall liquid measuring cup. If you don't have one, you can use any tall container your hand blender will fit in.
Once the cream has cooled, pour the cream mixture into the egg whites. Stick the hand blender in the mixture and swish it around a bit without turning it on to remove any air trapped near the blades. With the blender fully submerged, pulse until the mixture is homogeneous. The idea is to mix evenly without incorporating any air.
Divide the Panna Cotta custard between the ramekins and pour boiling water into the tray halfway up the sides of the ramekins.
Carefully put the tray into the oven and bake for 30 to 40 minutes or until the custard has reached 163 degrees F (73 C).
Let the ramekins cool, cover and refrigerate until set.
Run a hot paring knife or needle around the edge of the ramekin to separate and then unmold the Panna Cotta onto a plate.