In a large stockpot with a steamer basket, steam the trimmed broccoli florets for a couple of minutes or until bright green. Remove from heat and place the broccoli in a large bowl. Drain out the water.
Replace the pot on the stove, set to medium heat. Melt butter and add in the chopped onion and garlic, stir and cook until the onions become translucent, about 2 minutes.
Add in the rice flour and whisk until the flour starts to brown slightly. Slowly whisk in the chicken broth and simmer until the broth starts to thicken.
Add in the heavy cream, nutmeg, salt, and pepper.
Chop the steamed broccoli and add it to the pot, then simmer for 15 to 20 minutes.
Using a hand immersion blender, blend until smooth.
Serve with more sharp grated cheddar and broccoli florets.