Preheat the oven to 350°F and line an 8x8 inch pan with parchment paper.
Melt the butter and dark chocolate together in a saucepan over low heat, stirring until smooth.
Remove from heat and stir in the sugar, then add the eggs one at a time followed by the vanilla extract.
In a separate bowl, whisk together the flour, matcha powder, and salt.
Fold the dry ingredients into the chocolate mixture until just combined.
Pour the batter into the prepared pan and bake for 20 to 25 minutes until a toothpick comes out with a few moist crumbs.
Let the brownies cool completely in the pan before cutting into 8 squares.
Use the melted white chocolate to pipe hair and stitch details on each square, then press two candy eyes into place on each one.