Melt the butter in a skillet over medium heat and brown the chicken thighs on both sides, 5 to 8 minutes per side.
Remove the chicken thighs and set aside. In the hot skillet, cook and stir the onions until softened, about 5 minutes.
Pour the apricot halves, chili sauce, brown sugar, cinnamon, cardamom, ginger, and black pepper into a blender, and pulse several times to puree.
Pour the mixture into the skillet with the onions, bring to a boil, and reduce heat to a simmer. Simmer the sauce until slightly thickened, about 5 minutes. Return the chicken thighs to the sauce, and spoon sauce over the chicken. Simmer until the chicken is tender and no longer pink inside, 15 to 20 minutes.