To Make Toffee Bits:
Line an 8x10 inch rimmed baking sheet with aluminum foil, leaving at least 1-inch to overlap the top of the pan on all sides. Lightly coat the surface of the foil with butter or nonstick cooking spray. Attach a candy thermometer to a heavy bottomed sauce pan. Place the candy thermometer at least 1/2 inch off the bottom of the pan.
In a medium-sized, heavy saucepan combine the brown sugar, water, butter, and corn syrup. Over medium heat, bring the sugar mixture to a boil. With a heatproof pastry brush that has been dipped in warm water, wash down the sides of the saucepan to remove any sugar crystals that may have formed. Cook, without stirring, until the mixture reaches 285 F (soft-crack stage) on a candy thermometer. Immediately remove the saucepan from the heat and add the baking soda and vanilla extract and stir to combine.
Immediately pour this mixture into the baking sheet and allow to sit at room temperature until completely cool.
Once the candy has cooled, roughly break apart. Using a food processor, chop the toffee into small bits using pulse.
To Make the Cookies:
Heat oven to 375 F. Lightly grease cookie sheet or line with parchment paper. Using a stand mixer or hand mixer and a large mixing bowl, cream together butter and brown sugar until light in color and fluffy. Add eggs and vanilla and mix until well blended. Add flour, baking soda, cinnamon and salt; beat until blended.
Using a spoon or spatula, stir in oats, toffee bits and coconut, if desired. Drop dough by rounded teaspoons 2 inches apart onto prepared baking sheet.
Bake 8 to 10 minutes or until edges are lightly browned. Allow to cool on the baking sheet for 2-3 minutes then remove to wire rack to cool completely. About 4 dozen cookies