Preheat your oven to 375 degrees F. Line baking sheets with parchment paper.
In the bowl of an electric mixer fitted with the paddle attachment beat the brown butter (can still be in melted form), brown sugar and eggs until smooth and light in color, about two minutes. Scrape down the sides of the bowl.
With the mixer on low speed, add the flour, toasted oats, baking soda, baking powder and salt. Mix until combined.
Stir in the toffee chips
Scoop 2-inch balls of dough onto the cookie sheet. Bake for 6-8 minutes. The cookies are done when the edges are slightly golden brown. The top may look a little soft. That's ok! The cookies will continue to bake a little while they cool.