Preheat oven to 350 and line rimmed baking sheet with unbleached parchment paper. You may need two, depending on how large your baking sheet is.

Peel bananas and break into chunks. Using a fork, mash bananas until no chunks are left. Mix in nut butter and vanilla extract until well incorporated.

Add oats, flax, raisins, cinnamon, baking soda and salt to the bowl and mix well.

Taste the batter and add in 1-2 Tablespoons maple syrup, if you like a sweeter cookie.

Scoop onto prepared baking sheet. I like to use a mini scoop, but you can also use a teaspoon to scoop and the back of another to drop cookies onto sheet. Wet the back of a spoon and use it to flatten cookies onto sheet.

Bake for 10-12 minutes, until beginning to brown. Cookies will be soft, and firm up as they cool.

Transfer to a wire rack and cook completely before storing in air tight container.

Cookies will stay good in air tight container for a week, or in the freezer for up to 3 months.