Prep
Use a 10–12 oz microwave-safe mug.
Lightly grease inside of mug (optional but helpful).
If using frozen blueberries, do not thaw.
Mix Dry Ingredients
In the mug, combine flour, sugar, baking powder, and salt.
Stir well with a fork to evenly distribute.
Add Wet Ingredients
Add milk, melted butter (or oil), and vanilla extract.
Stir until smooth and no dry flour remains.
Add Blueberries
Gently fold in blueberries.
Do not overmix.
Microwave
Cook on high for 60–90 seconds.
Start with 60 seconds and check.
If needed, microwave in 10–15 second intervals.
Cool & Serve
Let rest for 1–2 minutes.
Top with powdered sugar, whipped cream, or ice cream if desired.
Serve warm.