Make the dipping sauce: 

1. Cut the limes in half and juice them.
2. Combine the lime juice, mayonnaise, minced garlic, fish sauce, sugar, cilantro, and chili.
3. Whisk to combine and set aside.

Prepare the shrimp:

1. With a pair of kitchen scissors, right below the head, snip a shallow cut down the center of the shrimp, until you come to the tail. Set aside and continue cutting the rest of the shrimp.
2. Use your fingers or a toothpick to pull out the intestines and grit from the back of the shrimp.
3. Dry the shrimp off with some paper towels and set aside.

Stove Top Technique:

1. Wrap a heavy shallow pan (mine is a staub 12” cast iron skillet that is 2.5 inches deep) with aluminum foil.
2. Pour the salt in the pan. Cover with a lid and heat over medium high heat for 5 minutes until you hear the salt popping. 
3. Take the lid off and lay the shrimp flat in the pan.
4. Again cover the pan with the lid and reduce the heat to medium. Cook the shrimp for 4-5 minutes. The bottom part should be a bright orange but the top will still look a little raw. Flip the shrimp over, cover with the lid, and cook for another 2-3 minutes.
5. Serve the shrimp in the pan or transfer to a plate and serve immediately with the dipping sauce on the side.

Oven Technique:

1. Preheat the oven to 400 and move the oven shelf to the center rack. Pour the salt onto a foil wrapped baking sheet (Mine is a quarter size) and shake gently to spread the salt. 
2. Put the tray into the oven and heat it for 8-10 minutes. The salt will start to turn a light golden color.
3. Carefully place the shrimp onto the salt in one layer. Put the tray back into the oven and roast for 7-9 minutes, flipping halfway through.
4. Serve the shrimp on the baking sheet or transfer to a plate with the dipping sauce on the side.