For the Cakes

1. Preheat the oven to 300 degrees.  Line a baking sheet with parchment paper and spread instant dry milk evenly over the paper.
2. Toast the dry milk for 3-5 minutes, watching closely, until it is golden brown in color.
3. Cool the toasted dry milk, and then stir into the buttermilk.
4. Turn the oven up to 350 degrees, and line a muffin tin with square shaped wells with paper liners*.  Lightly spray with nonstick baking spray.
5. In a medium bowl, sift together all-purpose flour, baking powder, and salt.  Set aside.
6. In the bowl of an electric mixer, cream together margarine, granulated sugar, and brown sugar with the paddle attachment on medium speed.  Add eggs one at a time, mixing in between additions.
7. Add vanilla extract and mix.
8. Reduce the speed to low, and alternate adding the buttermilk mixture and the flour mixture into the electric mixing bowl.  Do not overmix.  Use a spatula to scrape down the sides.
9. Fill each well 2/3 full of the batter.  Bake for 18-23 minutes, or until a toothpick inserted into the center of the cakes comes out clean.  Allow the cakes to cool in the pan for 5 minutes before removing, and another 15 minutes before glazing.

For the Glaze

In a small saucepan, melt margarine and brown sugar over medium heat.  Turn off the heat, and whisk in vanilla extract and powdered sugar.  Add 2-3 teaspoons of heavy cream and whisk until smooth and glossy. The consistency of the glaze is right when it slowly runs off the back of a spoon.  Dip each tea cake in the glaze, allowing excess to drip back into the saucepan.  The glaze will harden as it cools.