Preheat oven to 350 degrees. Butter 8 mini bundt cake molds. Sprinkle walnuts in bottom of molds, dividing equally. In a smaller bowl, combine flour, baking powder and salt. In a medium bowl, beat softened butter and sugar until fluffy. Add eggs, 2 at a time. Beat in vanilla and 10 tablespoons dark rum. Gradually beat in dry ingredients. Divide mixture between mini bundt cake molds. Bake for 20 to 25 minutes, until golden.
Combine 1/2 cup rum, 1/2 stick butter, water, sugar, orange juice and grated orange peel in medium saucepan. Boil until slightly thickened, about 8 minutes.
Invert warm cakes onto plates. Using a toothpick, poke holes into top of individual cakes (this will help absorb the syrup better). Pour warm glaze over warm cakes, dividing equally. Let cool slightly but serve warm. Garnish with mint sprigs and orange peel strips.
Recipe courtesy of Marcela Valladolid, Recipe Stylist, Bon Appetit Magazine