Preheat oven to 350°F.

Butter a 13 x 9-inch glass baking dish.

Bring water to a simmer in a small saucepan.

Reduce heat to low.

Add chopped German's chocolate and whisk until smooth.

Cool the chocolate mixture.

Sift flour, baking powder, and salt into a medium bowl.

Using an electric mixer, beat sugar and butter in a large bowl until blended.

Beat in egg yolks one at a time.

Beat in the cooled chocolate mixture and vanilla extract.

Beat in dry ingredients alternately with buttermilk.

Using clean, dry beaters, beat egg whites in another bowl until stiff but not dry.

Fold the egg whites into the batter in 2 additions.

Pour batter into the prepared dish.

Sprinkle with semi-sweet chocolate chips.

Bake until a tester inserted into the center comes out clean, about 55-60 minutes.

Cool cake in pan on rack.

Make Frosting: Combine evaporated milk, sugar, butter, and egg yolks in a heavy saucepan.

Whisk over medium-high heat until the mixture simmers, thickens, and leaves a path on the back of a spoon when a finger is drawn across, about 18 minutes.

Mix in coconut and pecans.

Spread warm frosting over cake.

Immediately sprinkle 1/4 cup of semi-sweet chocolate chips over the frosting.

Let stand until frosting sets, about 2 hours.

Cut cake into squares and serve.