Start by preheating the oven to 350°F (175°C). Line a 12-cup muffin tin with paper liners – give the top of the pan a light spritz with cooking spray too, just in case the muffins spill over while baking.

In a large bowl, mash bananas with a fork until they’re mostly smooth but still have some small lumps.

Pour the melted butter over mashed bananas while it’s still warm (but not hot). Mix them together – this helps the banana flavor spread throughout the batter. Add the eggs, milk, and vanilla, and whisk until everything’s well combined.

In a separate bowl, whisk together flour, sugar, baking soda, and salt. Make sure there are no clumps.

Add the dry ingredients to the wet mixture and stir just until you don’t see any dry flour anymore. The batter will be thick and a bit lumpy – that’s exactly what you want. Overmixing will make your muffins tough.

Very gently fold in the raspberries with just 2-3 strokes. Some will break up, and that’s okay – it’ll create pretty swirls in your muffins. If you’re using frozen berries, fold them in while still frozen to prevent bleeding.

Divide the batter between muffin cups. They should be quite full, about 3/4 of the way up. Use an ice cream scoop for even portions.

Bake for 22-25 minutes, or until the tops are golden brown. Insert a toothpick into the center of a muffin – it should come out clean or with just a few moist crumbs.

Let the muffins cool in the pan for about 5 minutes – they’re still setting up inside. Then transfer them to a wire rack. They might stick a bit to the liners while warm, so wait about 15 minutes before peeling if you want to eat them right away.