Pre-heat oven to 350 degrees F.
Put sugar and butter in a bowl. Add boiling water and stir to melt butter.
Sift chestnut flour, salt and baking soda into mixture. Blend thoroughly.
Add eggs and vanilla. Pour into 9-by-13-inch baking pan.
Bake for approximately 50 minutes or when a knife inserted into center comes out clean.
In a sauce pan, mix cornstarch and sugar.
Add butter and boiling water. Heat to a boil while stirring.
Add in chopped pecans and shredded coconut. Spread on cake.
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