Preheat oven to 375°F (190°C). Open and separate biscuit dough into 10 pieces as directed. Pinch each piece of dough in thirds (don't roll) to make 3 mini buns from each piece (for a total of 30 small buns). Place on parchment paper-lined baking tray, lightly brush each with water and sprinkle with 1/8 tsp (0.5 mL) sesame seeds. Bake until golden and cooked through, about 10 min.; let cool.
At the same time in oven, cook 30 meatballs according to package directions, 12 to 15 min., turning halfway through cooking time. While still hot, toss meatballs with 1/2 cup (125 mL) cranberry sauce and salt and pepper to taste.
Cut each bun in half. Spoon a little cranberry sauce on each bun bottom, top with 3 spinach leaves and a small slice of Brie cheese. Top each with a meatball, cap with bun top and secure with a small bamboo or wooden skewer.