To make the crumb topping, in a medium bowl, whisk the melted butter, brown sugar, granulated sugar, cinnamon, and salt for 1 to 2 minutes until the sugar starts to dissolve.
Stir in the flour with a fork until large crumbs form, then set aside.
To make the muffin batter. In a small saucepan over low heat, melt the peanut butter and butter, stirring constantly, until smooth, then remove from the heat and let cool slightly.
In a small bowl, whisk together the flour, baking soda, cinnamon, and salt.
In a large bowl, whisk the egg, brown sugar, and vanilla until smooth.
Whisk in the peanut butter mixture until smooth.
Stir in the flour mixture until almost combined; the batter will be very thick.
Add the milk and stir just until a batter forms, without overmixing.
Scoop the batter into the liners, filling each ¾ full.
Swirl 1 tablespoon of jam onto the top of each muffin.
Press a generous amount of crumb topping onto each muffin.
Bake for 22-25 minutes, until the crumb is golden.
Cool in the pan for 10 minutes.
Add dollops of jelly on top of the muffins before serving.