Before grilling the squid, I like preparing the sauce first so I can eat it with the squid right after it's cooked. In a small saucepan, melt the butter over medium heat. Add the minced garlic and cook for 30 seconds. Remove from the heat and add the soy sauce, sugar, and lemon juice. Whisk vigorously until the sauce becomes pale and creamy.
To clean the squid, pull out the tentacle and innards from the head. Use a knife to chop off right below the squid's eyes to separate the innards and tentacles. Discard the innards.
Remove the "plastic" beak from the head. Rinse under tap water and remove any leftover guts. The head should be more or less hollow. Use a knife to make a diagonal 1-inch criss-cross pattern on both sides of the head. Set aside.
Dry the head and tentacles thoroughly with paper towels.
Heat a cast-iron pan over medium-high heat until hot. Add the oil and swirl to coat the pan. Place the head in the pan and put a smash burger press on top to weigh it down. Grill both sides of the head for 2-3 minutes until charred on the outside. Do the same for the tentacles but for a bit less time.
Transfer the head and tentacles to a plate and pour the sauce overtop. Enjoy!