Pre heat oven to 375F,,grease and flour a 10 inch bundt pan. In small bowl mix banana and lemon juice..set aside..In a medium bowl mix cocoa, flour, baking soda. set this aside.
In a large beat oil and brown sugar until light and fluffy, beat in eggs one at a time add vanilla, blend half the flour mix and half the buttermilk beat 1 minute then beat the rest of the flour and the rest of the buttermilk, fold in bananas and 1/2 cup of the chocolate chips.
Spread into prepared pan bake until a wooden skewer inserted into the thickest part of the cake comes out with only a few moist crumbs about 55 minutes...cool in pan on rack for 30 minutes then turn out onto rack.
Glaze Melt remaining 1/4 chips with the milk in micro on high for 1 minute and whisk until smooth..drizzle over cake..You can double the glaze recipe if you want more glaze on top.