Preheat oven to 350 and butter/flour one 12-cup muffin pan (you can also use cooking spray). In a large bowl, combine flour, sugar, baking powder, and salt.
In a separate, smaller bowl, whisk together egg, vegetable oil, and milk.
Pour wet ingredients over dry ingredients and stir until just combined (a few lumps are ok!).
Spoon 2 tbsp of batter into each of the prepared cavities of the muffin pan, then place one tsp of strawberry jam in the center. Cover with another 2 tbsp of muffin batter, and use a toothpick or a spatula to make sure the jam is entirely covered by muffin batter.
Bake at 350 for 16-18 minutes or until the muffins spring back when gently pressed with a finger or a toothpick inserted into one comes out with only a few crumbs. Let cool in pan for five minutes before carefully removing and setting on a cooling rack.
Next, set up your dipping station. Place melted butter in a small bowl and sugar in a separate bowl. Quickly dip the outside of the muffin in melted butter, shake off excess, then roll completely in sugar. Set back on cooling rack. Repeat until all the muffins are coated.