Heat a large skillet over medium-high heat. Cook and stir chorizo with mushrooms and onion in the hot skillet until browned and crumbly, 5 to 7 minutes. Drain and discard fat. Combine diced tomatoes, chicken broth, and tomato paste in a Dutch oven over medium heat. Bring to a simmer and stir in the chorizo mixture and most of the crema, reserving a small amount to drizzle on top later. Cover and let simmer, stirring occasionally, until stew is the texture of a thick chili, at least 30 minutes. Preheat the oven to 350 degrees F (175 degrees C). Lightly butter both sides of the bread slices and place on a baking sheet. Toast in the preheated oven, turning bread halfway, for 10 minutes. Fill a pot with water and add baking soda. Bring to a boil. Add eggs and boil for exactly 5 minutes and 45 seconds. Remove eggs and immediately place into an ice water bath to stop the cooking process. Remove shells. Place eggs into the chorizo stew to re-warm them. Top with queso fresco and drizzle with the remaining crema. Serve in bowls with pieces of toasted bread.