Heat 1 tablespoon oil in a skillet over medium-high heat and sear chicken thighs 3-4 minutes per side until golden. Transfer to the crockpot.
2 lbs chicken thighs
Add diced onion, minced garlic, grated ginger, vindaloo spice mix, tomato paste, brown sugar, and chicken broth to the crockpot. Stir to coat chicken evenly.
3 tbsp vindaloo curry paste, 4 cloves garlic, 1 tbsp fresh ginger, 1 large onion, 2 tbsp tomato paste, 1 tbsp brown sugar, 1 cup chicken broth
Cover and cook on low for 3 hours until chicken registers 145°F on an instant-read thermometer. Avoid lifting lid during this time.
Stir in cubed potatoes, cover, and cook another 2-3 hours until chicken hits 165°F and potatoes are fork-tender.
2 medium potatoes
Remove lid, stir in white vinegar, and cook uncovered for 20-30 minutes to reduce sauce. Stir in coconut milk if using, then taste and adjust seasoning with salt or sugar.
0.25 cup white vinegar, 0.5 cup coconut milk