Preheat the oven to 350°F.

In a small bowl toss the chocolate chips and Grand Marnier until the chips are moistened and shiny. Add the 1-1/2 teaspoons flour and toss until evenly coated.

In a medium bowl lightly combine the eggs, 1/4 cup sour cream, and orange flower water or vanilla.

In a large mixing bowl combine the dry ingredients and orange zest and mix on low speed for 30 seconds to blend. Add the butter and remaining 3/4 cup sour cream. Mix on low speed until the dry ingredients are moistened. Increase to medium speed (high speed if using a hand mixer) and beat for 1-1/2 minutes to aerate and develop the cake's structure. Scrape down the sides. Gradually add the egg mixture in 3 batches, beating for 20 seconds after each addition to incorporate the ingredients and strengthen the structure. Scrape down the sides. Stir in the chocolate chips.

Scrape the batter into the prepared pan and smooth the surface with a spatula. Bake 55 to 65 minutes or until a wire cake tester inserted in the center comes out clean and the cake springs back when pressed lightly in the center. The cake should start to shrink from the sides of the pan only after removal from the oven.

Shortly before the cake is done, prepare the syrup: Heat the sugar, orange juice, and Grand Marnier until the sugar is dissolved. Do not boil. As soon as the cake comes out of the oven, place the pan on a rack, poke the top all over with a wire tester, and brush on 1/2 the syrup. Cool in the pan on the rack for 10 minutes, then invert onto a serving plate or cardboard round. Brush with the remaining syrup and cool completely before glazing with chocolate or wrapping airtight.