Preheat oven to 170C.

Grease pan, and line bottom with parchment paper.

Cream butter and sugar together until fluffy.

Add eggs and beat one at a time.

Beat on high for 1 minute to incorporate air into batter.

Add milk & vanilla extract and beat until combined.

Sift in flour, cocoa powder, and baking powder.

Beat until just combined.

Fold in milled/blended walnuts.

Pour into baking tin, drop tin on counter tops a few times to remove large air bubbles.

Bake at 170C for 50-55 minutes for 9 inch cake, or 40 minutes for 6 inch cake.

Check by inserting skewer into cake, if it comes out clean, it means it's done.