Preheat the oven to 180°C. Line 9x9-inch square baking pan with parchment paper, leaving extra paper on the sides to help lift the bars out later.
In a mixing bowl, cream together the softened butter and caster sugar until the mixture turns light and fluffy. Add the all-purpose flour, cornstarch and salt to the bowl and mix until you have a crumbly dough.Press the shortbread dough evenly into the bottom of your prepared baking pan. You can use your hands or the back of a spoon to do this.
Bake for 20-25 minutes, until the shortbread has a light golden colour around the edges. Once done, take it out ofthe oven and let it cool while you work on the pecan topping.
In a saucepan, melt the butter over medium heat. Stir in the brown sugar, honey, heavy cream, vanilla extract, and salt. Let the mixture come to a gentle boil, then reduce the heat and simmer for 2-3 minutes, stirring constantly. Add the chopped pecans to the caramel mixture and mix well.
Pour the pecan topping evenly over the baked shortbread base, using a spatula to spread it out. Return the pan to the oven and bake for an additional 20-25 minutes, until the topping bubbles and becomes golden brown.
Allow the pecan shortbread bars to cool in the pan for about 10-15 minutes. Then, use the parchment paper overhangs to lift them out of the pan and onto a wire rack. Let them cool completely.
If desired, melt the semisweet chocolate chips in a microwave for a couple of minutes, mixing every 30 seconds. Add a teaspoon of coconut oil. Alternatively, melt chocolate using the double boiler method. Drizzle the melted chocolate over the cooled bars and place in the fridge.
Once completely cooled, use a sharp knife to cut the bars into squares or rectangles.