In a heavy stockpot or braiser pan, heat olive oil over medium. Add garlic, saute until fragrant and soft, then add onion and fennel. Sprinkle with salt and let cook down until very soft, stirring frequently. Add tomato paste and stir to break it up. Add chicken stock, fennel seeds, salt and pepper. Let cook until bubbly. Reduce heat to a low simmer, then once it is simmering on low, swirl in heavy cream or half and half. Taste and season as needed. Remove from heat.