Preheat the oven to 350 degrees.
In a large bowl, cream together butter, brown sugar, white sugar, and peanut butter until smooth. A stand mixer or electric hand mixer works well.
Beat in the eggs until well blended. Combine the flour, baking soda, and salt; stir into the creamed mixture.
Mix in the oats until just combined.
Scoop cookies, using a medium cookie scoop, on cookie sheets lined with parchment paper.
Bake for 10 minutes.
Allow cookies to cool for 5-6 minutes before transferring them to a cooling rack.
Add a small spoonful (about a teaspoon) of peanut butter to the top of each warm cookie. Allow peanut butter to stand on cookies for a few minutes then spread over the cookie with a butter knife.
Microwave glaze (ganache) ingredients in a microwave-safe bowl in 20-second increments (for about a minute). Stir until completely smooth. Spoon ganache over cookies.