Pumpkin Spice Cake with Maple Buttercream

Cake

• 12 oz unsalted butter, room temperature, in pieces, plus extra to grease
• 6 oz sugar
• 6 oz brown sugar
• 8 oz whole milk, room temperature
• 4 large eggs
• 15 oz all-purpose flour
• 1 tbsp homemade pumpkin spice mix (see Tip)
  of 1 tbsp pumpkin pie spice
• 1 tsp baking soda
• 2 tsp baking powder
• ⅛ tsp salt

Buttercream Frosting

• 4 oz maple sugar
• 10 oz confectioners sugar
• 12 oz unsalted butter, softened and in pieces
• 1 tsp maple syrup
• 12 oz homemade pumpkin butter (see Tip)
  of 12 oz pumpkin butter