Let's take a closer look at the switch mechanism: In the 1st photo, you'll see that the switch is in the off position, as the black wedge is not in place within the appropiate notch etched into the golden piece.

In the 2nd photo, you can see the black wedge has been pushed into place within the golden piece. This is regularly accomplished after having pushed the red "push to start" button found on the metal frame where the egg cooker's label can be found. This process turns the machine on and initiates the cooking process.

Notice the bimetallic piece from Step 2 letting the gold piece hold the black wedge in the on position.

When the device heats up enough to cook the eggs, this bimetallic strip will bend in the direction of the green arrow, pushing the switch back into the off position, and turning the machine off.