Preheat the oven to 350°F. Spray a standard bundt pan with baking spray or butter and flour. Set aside.
Using an electric mixer, cream together the butter, peanut butter and vanilla. Beat until completely smooth.
Add the granulated sugar and brown sugar. Beat until fluffy and combined on medium-high for 2-3 minutes.
Add the eggs one at a time beating well after each addition.
Sift together the flour, baking powder and salt. Turn the speed of the mixer to medium and add the dry ingredients alternately with the buttermilk.
After all has been added, scrape the sides of the bowl then beat for 1 minute or just until fully combined.
By hand, mix-in the Reese's, milk chocolate and peanut butter chips. (Reserve 1/2 cup of chopped Reese's for garnishing)
Spread evenly into the bundt pan. Bounce on the counter a few times to settle the batter.
Bake for 1 hr 15 to 1 hr 30 minutes OR until a tester inserted into the center comes back clean. Check halfway through baking and lay a piece of aluminum foil on top to prevent over browning, if needed.
Cool in the pan for 20 minutes then carefully turn onto a cooling rack to cool completely.
To make glaze: In a medium-size microwave safe bowl melt together the chocolate chips, heavy cream and peanut butter. Heat in 20-30 second increments stopping to stir each time.
Add additional cream as needed, until pourable.
Drizzle over the cooled cake then sprinkle with reserved chopped Reese's cups.
Store tightly sealed chilled or at room temperature.