Preheat oven to 350 degrees. Lightly grease and flour three 3-inch by 5-inch mini loaf pans
In a medium bowl, combine 1 cup plus 2 tablespoons of the cake flour with the cornstarch and baking powder.
In bowl using an electric mixer, beat 1 cup sugar, 1 cup plus 2 tablespoons of the butter, 1/2 teaspoon vanilla, and the lemon extract for about 5 minutes, or until light and creamy. Add the eggs one at a time, beating well after each addition, and adding 2 to 3 tablespoons of the flour mixture with the last egg; the mixture may seem curdled but it isn't. Beat for 3-4 minutes, or until creamy again.
With a rubber spatula, fold in the remaining flour mixture until thoroughly mixed. Stir in the chocolate chip.
In a small bowl, with a fork, mix together the remaining 1/4 cup sugar, 2 tablespoons butter and 3/4 teaspoons vanilla. Add the remaining 1/2 cup flour and mix until crumbly.
Fill the prepared loaf pans with the crumb cake batter and sprinkle the crumb mixture over the top.
Bake the cakes for 35 to 40 minutes, or until the middle of the cake springs back when touched lightly or a toothpick inserted in the center comes out clean.
I don't like lemon and chocolate so omitted the lemon extract! I also LOVE mini chocolate chips so used those instead of regular sized ones!!!