Preheat your oven to 350°F (175°C). Grease a muffin tin.

Melt the unsalted butter in a medium saucepan, cooking until golden brown (5-7 minutes).

In a mixing bowl, cream the browned butter with dark brown sugar and granulated sugar until light and fluffy (3-5 minutes).

Mix in the egg and vanilla extract until fully combined.

In another bowl, whisk together flour, baking powder, baking soda, and salt. Fold into the wet ingredients until just combined.

Scoop the dough into the greased muffin tin, filling cups about two-thirds full and pressing lightly.

Bake for 12-15 minutes until edges are golden brown and centers are slightly soft.

Remove from the oven and cool in the pan for 5 minutes before transferring to a wire rack.

Fill each cup with pistachio cream spread and allow it to overflow slightly.

Garnish with powdered sugar or melted dark chocolate and serve warm or at room temperature.