A brown butter muffin is a deep muffin. A brown butter muffin dotted with magenta berries and crunchy black cacao nibs is a bold yet sophisticated muffin. Here I took a base recipe for coffeecake rye flour muffins plucked from a newspaper article on whole grain baking by Kim Boyce and opted to (gasp) omit the crumble topping and swap in berries and cacao. The vanilla brown butter, however, wasn't going anywhere. —Two Trays Kitchen
Grease about 10 wells of a muffin tin and heat the oven to 375, rack in the middle.
Allow the butter to melt, stirring occasionally, until the foam has subsided and the milk solids have dropped to the bottom of the pan and browned (don’t let them get too dark). Remove from heat and immediately pour browned butter, including flecks, into a heat-proof bowl to stop the cooking. Allow to cool slightly.
In a large bowl, stir together the rye flour, all-purpose flour, sugar, baking powder, baking soda, salt, cinnamon.
Whisk yogurt, egg and vanilla extract together into the slightly cooled butter. Add the wet ingredients to the bowl of dry ingredients and fold and gently stir until just combined. Fold in half the berries and about 1/3 of the cacao nibs.
Evenly scoop batter into prepared tin about 2/3 full. Stud each muffin with the remaining raspberries, sprinkle evenly the cacao nibs and give each a little shower of raw sugar.
Bake 10 minutes at 375, then turn the oven to 350 for about 15 more minutes, about 25 minutes total, or until golden brown and the tops spring back when lightly touched and a skewer comes out clean.
Let the muffins cool slightly in the tin, then pivot them onto their sides to ensure a dry, not soggy, crust. Continue to cool by themselves on a wire rack.