Heat oven to 175C (350F) Line 8×8 baking pan with parchment paper. Combine flour, oats, brown sugar, baking soda, and salt in large mixing bowl. Cut in butter until mixture is crumbly (I found it useful here to use my hands and a knife, but whatever works for you). Press half the mixture into pan. Bake for 10 minutes. This solidifies the base so the caramel doesn’t seep through too much. While baking, make caramel. Melt 1/2 cup sugar in medium heavy bottomed pan over medium heat. Take your time, stirring the melted sugar towards the center as it melts. Don’t over stir. When sugar is completely melted and turns amber, remove from heat and add half the cream and salt. If caramel seizes, return to low heat and stir till sugar melts again. Add in remainder of cream. Finally add in speculoos. Stir until smooth. Pour on top of partially baked oatmeal bar. (Here’s where you would add the white chocolate chips if you so fancied.) Add remaining oatmeal mixture. Bake for 20-25 minutes until golden. Let cool and cut – yum!