Preheat your oven to 350°F (175°C) and line a muffin tin with parchment paper liners or grease it lightly.
In a large mixing bowl, whisk together the melted coconut oil or butter, honey, and vanilla extract until well combined. Next, add the buttermilk, Greek yogurt, and eggs. Whisk until the mixture is smooth and creamy.
In another bowl, mix together the all-purpose flour, white whole wheat flour, baking powder, and kosher salt. Stir until well combined.
Gradually add the dry ingredients to the wet mixture, stirring gently with a rubber spatula until just combined. Be careful not to overmix. Fold in the creamy peanut butter until evenly distributed.
Gently fold in the raspberry or strawberry jam, creating swirls throughout the muffin batter for those delightful bursts of flavor.
In a small bowl, combine the old-fashioned oats, all-purpose flour, brown sugar, cinnamon, and cubed salted butter. Use your fingers or a fork to mix until crumbly.
Scoop the muffin batter into the prepared muffin tin, filling each cup about two-thirds full. Top each muffin with a generous sprinkle of the streusel mixture.
Place the muffin tin in the preheated oven and bake for 20-25 minutes, or until the muffins are golden brown and a toothpick inserted into the center comes out clean.
Once baked, remove the muffins from the oven and allow them to cool in the pan for about 10 minutes. Then transfer them to a wire rack to cool completely. Enjoy your PB&J Oat Streusel Muffins warm or at room temperature!
