Use lowest carb vanilla ice cream.

chop up an Atkin's peanut butter chocolate bar.

drizzle a tiny bit of sf vanilla on the peanut butter/choc bits.

then mix the chopped peanut butter bar into lowest carb pb ice cream.

this can be as low as 5 carbs! unfortunately it's not low cal so you need to use 1/2 the atkins bar if you want to cut down a lot on cals.