Melt 2 tbsp marg in skillet over low heat. Add onions, ½ tsp. salt and thyme; cook until tender and lightly browned (30min)
Place one rack in upper third of oven and another in lower third, preheat oven to 400. Coat 2 baking sheets with cooking spray.
Mix flour, baking powder, sugar and remaining ½ tsp salt in bowl. Cut remaining 6 Tbsp marg into small chunks and add to the flour mix. Cut in marg using your fingers-until mix resembles coarse meal. Stir in milk with fork just until flour is evenly moistened.
Turn dough onto floured surface and pull together into one piece with floured hands. Divide dough into 48 mounds (about ½ Tbsp each) roll each into a ball and place on baking sheets. With a tsp measuring spoon, press an indentation into center of each ball. Spoon onion mix into indentations.
Bake-rotating pans halfway through, until golden 12-15 min.