For the Cake:

1. Preheat oven to 325°F (163°C). Grease and flour a 12-cup Bundt pan or spray with cooking spray.
2. Beat the butter with an electric mixer until creamy. Gradually add brown sugar and granulated sugar, beating until light and fluffy.
3. Add eggs one at a time, beating well after each addition.
4. In a separate bowl, whisk together flour, baking powder, and salt.
5. Alternately add the flour mixture and milk to the butter mixture, starting and ending with the dry ingredients. Mix until just combined.
6. Fold in toffee chips and chopped pecans.
7. Spoon batter into the prepared Bundt pan and spread evenly.
8. Bake for 85 minutes, loosely covering with foil after 45 minutes to prevent excess browning. A toothpick should come out clean when inserted.
9. Cool for 10 minutes in the pan before turning it out onto a wire rack to cool completely.

For the Caramel Drizzle:

1. In a medium saucepan, combine sweetened condensed milk and brown sugar. Bring to a boil over medium-high heat, whisking frequently.
2. Reduce heat and simmer for 8 minutes, whisking frequently until thickened.
3. Remove from heat and stir in butter and vanilla. Let cool for 5 minutes, then drizzle over the cooled cake.