Lightly butter a cookie sheet. In a heavy saucepan, combine the sugar and corn syrup with ¼ cup water. Bring to a boil and cook until the mixture reaches the soft crack stage (250°). Add the butter and pinions. Return to the heat and cook to the hard crack stage (295°). Remove from the heat. Stir in the baking soda. Pour the brittle quickly over the oiled pan and spread as thin as possible wit a spatula. When the candy begins to harden, flip the brittle until completely cooled. Break into irregular pieces. Store in airtight containers.