Preheat oven to 170°C (340°F). In a bowl, combine brown sugar, white sugar, flour and salt. Add cold butter and mix until the mixture resembles wet sand. Set aside.
2
In a large mixing bowl, beat butter, brown sugar, white sugar and oil until pale yellow. Add eggs one at a time, mixing well after each addition. Add vanilla extract and instant coffee, and mix thoroughly.
3
Sift in cake flour (or all-purpose flour), baking powder and salt. Gently fold together until just combined. Add milk and mix well.
4
Grease a 7×7 inch baking pan with oil or butter and line with parchment paper. Pour in the batter and top with the crumble mixture. Bake in the preheated oven at 170°C (340°F) for 30 to 35 minutes until a toothpick inserted comes out clean.
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