Cream the 1/2 C room temperature butter, sugar and eggs. Add sourdough discard, stirring well. Next add flour, powder, soda, salt and mix until well combined. Finally, add in 1/4 C of the milk, give it a good stir. You want this to be like a thick sticky muffin batter. Add a little more milk if needed to get sticky texture. Spread into a greased 8x8 square baking dish.
Combine all ingredients for topping into a bowl and mix well until crumbly texture. Pour out onto batter and spread evenly.
Bake in a 350 degree oven for 45-50 minutes until golden brown and a knife inserted in the center comes out clean.