1. Heat a saucepan and add 1 tablespoon oil and onions, carrots, celery and hot chili, if using. Cook for 2-3 minutes. Add the mushrooms and garlic and cook until vegetables are starting to brown, stirring often.
2. Add the additional 1 tablespoon of oil or butter and melt. Stir in the rice flour, or other thickener, and stir constantly to make a roux. This just means the flour is cooking in the fat, while you stir with a wooden spoon in a figure eight motion until the flour starts to look lightly tan and bubbly. This should take about 3 minutes or so.
3. Slowly whisk in 1 cup of the warm vegetable stock. Then add the poultry seasoning, thyme and sugar as you continue whisking. Then slowly add 2.5 more cups of vegetable stock, whisking until incorporated. Bring to a simmer for 5-10 minutes until vegetables are very soft and gravy is thickened a bit.
4. Take off the heat and carefully transfer to a small blender (I used my Nutribullet) or food processor. Blend until smooth. You may need to add a tablespoon or 2 of water to get it to desired consistency. Add salt and pepper to taste.