Preheat oven to 325°. Grease and flour a 10-inch fluted cake pan.
In a large bowl, whisk together the 1 ½ cups milk, the vegetable oil, and eggs.
Add flour, granulated sugar, baking powder, and salt; whisk to combine.
Stir in poppy seeds.
Pour into prepared pan and bake until a toothpick inserted in the center comes out clean, about 1 hour 10 minutes.
Remove from the oven and let cool 10 minutes in the pan before gently unmolding it onto a wire rack.
Place powdered sugar in a medium bowl.
For thick, white glaze, whisk in 2 tablespoons milk and vanilla. Spoon over cooled cake.
For a thin glaze that seeps into crevices, increase milk to 4 tablespoons. Pour glaze over cake when glaze is still warm to the touch, then let set.
