Preheat oven to 350°.

Cream butter and sugar. Drop the eggs in slowly, one at a time.

Fold in yogurt, vanilla extract, and espresso powder.

In a separate bowl combine flour, baking powder, baking soda, and salt.

Slowly fold dry ingredients into wet ingredients until combined.

Grease a large baking dish with butter or non stick spray. Pour in batter and level off.

In a separate mixing bowl combine remaining flour, butter, oats, and brown sugar. Toss.

Press together with your fingers and flatten to make long thin "clumps"

Spread topping over batter and spread out evenly.

Bake for approximately 40 minutes or until bubbly.