Follow these simple steps for microwave muffin perfection:

1. Choose Your Vessel: Select a standard-sized microwave-safe mug (around 10-12 oz capacity). Ensure it’s large enough for the muffin to rise without overflowing. Greasing the inside lightly with oil or cooking spray is optional but recommended for easier removal if you don’t plan to eat it directly from the mug.
2. Mix Dry Ingredients: Add the all-purpose flour, granulated sugar, baking powder, and salt directly into the mug. Use a fork or a small whisk to combine them thoroughly, ensuring there are no clumps, especially of baking powder.
3. Add Wet Ingredients: Pour the milk, vegetable oil (or melted butter), and vanilla extract into the mug with the dry ingredients.
4. Combine Gently: Stir the wet and dry ingredients together using the fork until just combined. Be careful not to overmix! A few small lumps remaining in the batter are perfectly fine. Overmixing develops the gluten in the flour too much, which can lead to a tough or rubbery muffin – the arch-nemesis of microwave baking.
5. Fold in Blueberries: Gently fold the fresh or frozen blueberries into the batter. If using larger berries, you might want to use slightly fewer. Try to distribute them evenly without excessively stirring.
6. Microwave: Place the mug in the center of your microwave. Cook on high power. Cooking time will vary depending on your microwave’s wattage:
   • 900-1000W: Start with 70-80 seconds.
   • 1100-1200W: Start with 60-70 seconds.
   • Lower Wattage (<900W): May need 90 seconds or slightly longer.
     The muffin should puff up significantly. It’s done when the top looks mostly dry and springs back lightly when gently touched. A toothpick inserted into the center (avoiding a blueberry) should come out clean or with moist crumbs attached, but no wet batter. Be cautious not to overcook, as this is the primary cause of dryness or rubberiness in microwave muffins.
7. Rest is Best: Carefully remove the hot mug from the microwave (use an oven mitt!). Let the muffin rest in the mug for 1-2 minutes before eating. This crucial step allows the residual heat to finish cooking the center gently and lets the structure set, resulting in a better texture.
8. Enjoy! Eat the warm muffin directly from the mug with a spoon, or carefully run a knife around the edge and invert it onto a small plate.