In a bowl, beat together the peanut butter, brown sugar, bicarb and salt.
Beat in the egg and vanilla extract, but not too vigorously: just to mix them; gently does it.
Stir or fold in the chocolate chips, then line 1 or 2 baking sheets with baking parchment.
Scoop out heaped tablespoonfuls of the cookie dough onto the lined sheets, placing them about 5 or 6cm apart, then bake for 10 minutes, until they're slightly darker around the edges. They will look undercooked but will be the perfect texture once cooled (if you can wait that long).
At any rate, leave them on the baking sheets for 10 minutes, as they will be very fragile. Then transfer gently to a wire rack to cool. This takes another 10 minutes; I tend to cave in after 5.