Note: these muffins are going to be denser and richer than your normal “muffin” – but since peanut butter is a thick and rich ingredient, there isn’t much way around the loads of flavor unless you want to use a peanut butter extract. The key is to work quickly here before the peanut butter starts to firm up again, so I suggest measuring out all of your ingredients before starting.
Preheat the oven to 350 degrees F. Place the butter and peanut butter together in a bowl and microwave for 30 seconds, stirring well. If the entire mixture is not melted, microwave in 15 second increments, stirring well after each, until it is. Set aside to cool slightly.
In a bowl, whisk together the flour, baking soda, salt and spices. Set aside. Line a muffin tin with liners. Spray the liners with nonstick spray – this will help keep the thicker crumbly dough together. You actually don’t even need to use liners as long as you spray the tin well, let the muffins cool completely and gently lift them out with a spoon.
In a large bowl, whisk together the egg, brown sugar and vanilla extract until smooth. Stir in the butter and peanut butter, mixing until smooth – the batter will be slightly thick. Add in the dry ingredients and stir until almost combined (it will be very thick) then add in the milk and stir until a batter forms, trying not to overmix. Fill the liners 3/4 of the way full. Use an ice cream scoop or equal measure for each. Press a tablespoon or so of the strawberry preserves into the center of the batter, pushing it into the middle. It’s okay if it goes down the sides! Press the tops of each generously with the crumb topping. Bake for 18 to 22 minutes. Let cook before trying to remove the muffins if you did not use a liner – if you did use a liner, try to let them cool before peeling the liner off.