1. Preheat oven to 325°F with the rack in the middle.
2. Butter and lightly flour an 8½" by 4½" loaf pan.
3. Heat Plugrá Butter in a 10-inch heavy skillet over medium-high heat until milk solids on the bottom are dark.
4. Chill for about 15 minutes, or until butter starts to thicken.
5. Whisk together flour, baking powder and salt. Stir in the ground and chopped nuts.
6. Beat together the brown butter, brown sugar and granulated sugar with an electric mixer until fluffy, about 2 minutes.
7. Add eggs, one at a time, beating well after each addition.
8. Beat in the cream and vanilla.
9. At low speed, mix in flour mixture until just incorporated.
10. Transfer batter to loaf pan, smoothing the top, then shake on counter to even the batter.
11. Bake until golden brown and a wooden pick comes out clean when inserted in the center, about 1 to 1¼ hours. Cool in pan for 30 minutes, then invert cake onto a rack and cool completely, right side up, for about 1 hour.
12. Slice and serve with Caramelized Mango-Mint Gloss.