For the caramel heat a heavy-duty 4-quart saucepan, sprinkle the sugar on its dry hot surface and cook on low barely stirring only when the inner layer of sugar starts to melt, mix the liquified sugar with the crystallized sugar on top of it very gently. Don't overstir. When all of the sugar is liquified, continue cooking on low stirring until the caramel is penny-bronze in color. Don't overheat it, burned caramel is no fun to eat:) while the caramel is still hot, add a pinch of salt, then carefully stir in the heavy cream (cause it will sizzle and spit), mixing vigorously in order to incorporate all of the cream into the caramel so the mixture is lump-free. If you are left with a few lumps of hardened caramel however, place the mixture on low heat again and cook stirring until all the lumps are melted. Take off heat to cool slightly.
Dissolve the cornstarch in 50ml whole milk, leave to rest.
Add the leftover milk to the caramel liquid, place on medium again, bring to an almost boil, add the cornstarch milk and cook constantly stirring until thickened. Take off heat, add the cream cheese, stir until glossy and smooth. Cool to room temperature, then transfer into the fridge overnight.
Freeze in your ice cream maker according to the manufacturer's instructions adding crushed biscoff or speculoos cookies at the last couple of minutes of churning. Store in an airtight container in the freezer or spoon right away.