Preheat the oven to 425 F. Grab a muffin tin and line with 6 liners. Set aside.
In a small bowl, combine the brown sugar, flour and melted butter for the streusel topping. Use a spoon to mix everything toghether until it forms a crumble. If it's still too dry, add a bit more melted butter. Set the bowl aside.
In a medium bowl, add the melted buter, milk, sugar, vanilla, greek yogurt and the egg and whisk them together.
In a separate bowl, combine the flour, salt, baking powder, cardamom, and chocolate chips.
Pour the dry ingredients into the wet bowl and mix to combine. Stop mixing as soon as there are no more flour streaks!
Scoop the batter into each liner until ¾ths full. Top with the brown sugar streusel and a few more mini chocolate chips, bake for 5 minutes at 425 F, then lower the heat to 375. Bake for another 15-17 minutes, or until the tops spring back when touched.
Let cool and enjoy!