Preheat your oven to 375°F (190°C) to ensure even baking.
Grease your muffin tin or line it with paper liners to prevent sticking.
In a mixing bowl, whisk together the egg, milk, and oil until well combined.
In another bowl, whisk together the all-purpose flour, sugar, baking powder, and salt.
Gradually add the dry ingredients to the wet mixture, stirring gently until just combined. Be careful not to overmix!
If using, gently fold in blueberries or jelly into the batter now.
Spoon the batter into the prepared muffin tin, filling each cup about two-thirds full.
Place the muffin tin in the preheated oven and bake for 18-20 minutes, or until a toothpick comes out clean.
Allow the muffins to cool in the tin for a few minutes before transferring them to a wire rack to cool completely. Enjoy warm or at room temperature!
