Measure out and prepare all the ingredients. Wash the spinach and cauliflower, if needed. Pat dry with a paper towel.

Add the ground beef chuck to a bowl and season with salt and pepper.

Create patties with your hands that are about 1/2" thick.

Using a saucepan over medium heat, put the spinach in and cook for 2 minutes until the spinach gets wilty.

Drain the spinach and pat it with a paper towel to remove as much water as possible. Chop the spinach up into tiny pieces.

Transfer spinach to a bowl.

Add the mozzarella cheese and grated parmesan cheese to the bowl.

Top half of the patties with the spinach, mozzarella, and parmesan cheese mixture.

Cover the patties with the other half.

Seal the edges of the two patties together and press down firmly to flatten the patties.

Using a pan over medium heat, grill the burgers for about 6 minutes on each side.

While the burgers are cooking, prepare the cauliflower rice by combining the riced cauliflower and half of the butter in a saucepan and cook over medium heat for 6 - 9 minutes. Stir well.

Once cooked, add the rest of the butter and sour cream. Stir to combine well. Season with salt and pepper.

Serve the burgers with the cauliflower rice and enjoy!