This muffin batter can be made the night before baking, or can be baked right away.

Brown the butter

Set the butter in a small pan over medium heat. Cook as the butter melts, then foams and sputters. You’ll start to see tiny cream colored bits at the bottom, stir so the butter browns evenly, and cook until those bits turn medium brown. Once all of them have browned and the butter smells nutty, immediately transfer the butter to a heatproof bowl - making sure to scrape down every bit from the pan.

Make the batter

Add the spices, salt and vanilla to the butter and stir. Leave to cool, at least 10 minutes.

Add the sugar and whisk very well, for at least 30 seconds. Crack in the eggs and whisk until the mixture is light and creamy. Add the pumpkin puree and sour cream and whisk to combine.

Add the flour and baking powder and soda and whisk to just combine. You have the option to proceed immediately or you can cover the bowl with plastic wrap to seal and bake it the next morning.

Make the streusel

Whisk together the dry ingredients (the flour, sugar, spices and salt) then slice the butter into tiny pieces over it. Using your fingers, work the butter into the flour so that it coats all of the flour. When you can squeeze the mix together and it clumps, it’s likely done mixing. Press it into the bowl. You can set it in the fridge to chill now if you aren’t using it right away.

When you’re ready to bake

Preheat the oven to 400 F. Line every other muffin cup with a muffin liner. Scoop the muffin batter into the cups, filling them ¾ full. Generously add the streusel on top, packing it onto the muffin batter.

Set the tins in the oven and immediately lower the temperature to 350 F. Bake the muffins until the middle tops spring back or a cake tester inserted into the center comes out clean, for about 20 minutes