Streusel

1. Spray a 9 x2 inch round cake pan with non-stick baking release.  Set aside.
2. Cut the butter into small pieces. 
3. Combine the flour, oats, and brown sugar in the bowl of a mixer.
4. Add the butter.
5. Beat on medium until crumbs form.  Be careful not to overbeat and turn it into a paste. 
6. Refrigerate while preparing the cake layer.

Irish Cake Layer

1. Preheat the oven to 350°F.  Spray a 9x2 inch round cake pan really well.  Set aside.
2. Peel, core and slice the apples very thinly. 
3. Place in a bowl and cover directly with plastic wrap.  They may still brown a bit, but that is fine.
4. Whisk the flour, baking powder, cinnamon and salt together in a bowl.  Set aside.
   
5. Without cleaning the mixing bowl, cream the butter, sugar and vanilla in the bowl of a mixer until light and fluffy. 
6. Beat the eggs in one at a time. 
7. They will most likely curdle. 
8. Add half the flour mixture and beat on medium low.
9. Add the milk.
10. Add the remaining flour.
11. Spread the batter in the prepared pan. 
12. Place the apples on top in a flat layer. 
13. Cover the apples with an even layer of streusel.
14. Bake for about 65 to 75 minutes.  A tester will come out cleanly and the apples will be soft.
15. Cool the cake in the pan.  
16. To serve, dust with powdered sugar, cut into slices and get ready for a real treat. 
17. Store the cake, covered, at room temperature for 3 to 4 days.  Ours barely lasted until the next day!!