Begin by seasoning the boneless, skinless chicken breasts generously with salt and pepper.

Heat a skillet over medium heat and add a drizzle of olive oil. Once the oil is shimmering, add the minced garlic, sautéing for about 1 minute until fragrant.

In a medium bowl, combine the soy sauce, chicken broth, and Marsala wine, whisking until well blended.

Place the seasoned chicken in the bottom of your crockpot. Pour the sauce mixture over the chicken, ensuring it is well-coated. Scatter sliced fresh mushrooms on top.

Cover the crockpot with its lid and set it to cook on low for approximately 6 hours or on high for about 3 hours.

Once the cooking time is complete, gently stir in the heavy cream just before serving.