Preheat oven to 450F on the convection setting (or 475F in a standard oven). Add the sliced mushrooms to a food processor and pulse until finely diced. Remove and set aside, then add the onion and bell pepper to processor and pulse until finely diced.

Add all of the burger ingredients to a large mixing bowl. Line a baking sheet with foil. Sprinkle the foil liberally with kosher salt to help absorb any grease that drips off the burger and prevent it from burning.

Form the patties and place on a cooling rack over the salted baking sheet. (There should be a little bit of meat leftover). Bake for 19–22 minutes in a convection oven (20–25 minutes in a standard oven). Watch the burgers closely towards the end, as they can overcook quite quickly.

Add the reserved meat mixture to a pan over medium heat, breaking it up as it cooks down.

Add the spinach, salt, pepper, and red pepper flakes. Let the spinach wilt down.

Add the roasted almonds and cook for another minute or two. Add the butter, cream cheese, and heavy cream. Stir them into the spinach until melted and well combined. Turn the heat down to very low to keep the spinach warm.

Remove the burgers from the oven — they should be nicely browned on top. Serve the patties alongside the spinach. Serve with dressing!