In a large bowl of cold water, add the dried shrimp shells. Move the shrimp around with your fingers and remove any foreign objects floating at the top.
Scoop up the floating shrimp shells and put them into another bowl. Do not scoop up anything from the bottom of the bowl as this is where any impurities/dirt will be.
Repeat this process at least two more times (so three times in total) to ensure all debris has been removed.
Strain the remaining shrimp shells, then use a spoon to press down on the shrimp shells to force any excess water out. Let it sit for a few minutes to further drain/dry.
In a cold fry pan, add the oil and garlic. Turn the heat to medium.
Once the garlic starts to colour, add the shrimp shells, salt, sugar and fish sauce. Mix well.
Keep stirring the shrimp shells around the pan for roughly nine minutes or until all liquid has been absorbed/evaporated.
Taste check and adjust to your liking.
Right before serving squeeze over the lemon juice, then serve with jasmine rice.