Heat 1/2 cup of sugar in a 1-qt heavy bottomed saucepan over medium-high heat, swirling pan often, until sugar dissolves and turns to liquid caramel.

Remove from heat; add 1/4 cup boiling water. Return pan to heat; cook, swirling pan gently, until caramel dissolves in water.

Remove from heat and let cool.

Transfer to a food processor along with remaining sugar, shallots, lemongrass, oil, soy sauce, fish sauce, pepper, and garlic; puree until smooth.

Place pork chops in a 9″ × 13″ baking dish and pour over puree; cover with plastic wrap and chill overnight.

Heat a 12″ cast-iron grill pan over high heat. Working in batches, add chops; cook, turning once, until charred in spots and cooked through, about 2 minutes. Serve immediately with rice and chili-garlic sauce.