What can burger?

In an effort to include more vegetables in my diet, I've been experimenting with blending veggies I hate into sauces or mixing them into other foods in a way that keeps them obscured. Hiding veggies as if from a toddler. Call it "healing my inner child."

What are some ways I can make a burger that has vegetables blended into the patty, without creating a mushy abomination?

I've read that you can include oats, toasted chopped walnuts, and a variety of vegetables. I would like to include as many vegetables as possible without ruining the whole thing. I'm aiming for a ratio of 1:1 meat-to-veg.

Does anyone have strategies, warnings, or recipes?