Preheat the oven to 350?F
In a large bowl, beat the butter, peanut butter and brown sugar until creamy; beat in the egg and vanilla.
Add the flour, oats, baking soda and salt and beat on low or stir until the dough comes together. Stir in the chocolate chunks.
Drop by the large spoonful onto a parchment-lined baking sheet and bake for 15 minutes, or until golden – darker around the edges, but still soft in the middle. Transfer to a wire rack to cool. Makes about 1 1/2 dozen large cookies.