In a small bowl, combine the mustards, honey, and 2 teaspoons of the olive oil.
In a sautÃ© pan or cast iron skillet, add 1 teaspoon of olive oil. Add the onion and sautÃ© over medium heat until golden and tender, about 5 minutes. Add the garlic and sautÃ© for an additional 1 - 2 minutes, until fragrant.
Place the chicken tenderloins on top of the onion and garlic mixture, or if the pan you cooked the onion and garlic in is not oven safe, transfer the onion and garlic to an oven safe dish and add the chicken to it. Salt and pepper the tops of the chicken according to your personal preference.
Pour the honey mustard mixture on top of the chicken. Arrange the rosemary sprigs around the chicken in the pan.
Bake the chicken at 375 20 minutes or until done, occasionally basting the chicken with the sauce.
Notes: Chicken thighs also work well. I have also used pork chops, but I brown both sides of the chops first before baking.
Having a really busy or lazy day? Skip the onion and garlic steps completely. Just stir the honey, mustards, and all 3 tsp of olive oil together. Proceed with the rest of the recipe.