Bring a large pot of heavily salted water to a rolling boil - it should taste like the ocean. Add your pasta and cook 2 minutes less than the package directions say. This seems weird, but trust me - the pasta finishes cooking in the sauce and you won't end up with mush. Before draining, scoop out 1 full cup of that cloudy pasta water and set it aside in a measuring cup or mug. This is liquid gold for your sauce. Drain the pasta but don't rinse it - that surface starch helps the sauce cling to every piece.

Cut your chicken breasts into bite-sized pieces - roughly 1-inch chunks work best. Season them generously with salt, pepper, and Italian seasoning. Don't be shy with the seasoning. Heat olive oil in a large skillet over medium-high heat until it shimmers. Add the chicken pieces in a single layer - don't overcrowd the pan or they'll steam instead of brown. Cook for 6-7 minutes, flipping once, until golden brown and the internal temperature hits 165°F. Remove the cooked chicken to a plate and don't wipe out the pan. Those browned bits stuck to the bottom? That's flavor waiting to happen.

Lower your heat to medium and add the minced garlic to that same skillet with all the chicken drippings. Cook for just 30 seconds, stirring constantly, until it smells amazing but hasn't turned brown. Burned garlic is bitter - we don't want that. Pour in the heavy cream and bring it to a gentle simmer. Don't let it boil aggressively or it might break. Stir in your pesto - as much as you want, honestly, but 1 cup is a good starting point. Now here's the magic: add about half of your reserved pasta water and whisk everything together until it's smooth and creamy. The pasta water helps the pesto and cream emulsify into a silky sauce instead of staying separated and oily. The sauce should coat the back of a spoon but still be pourable. Too thick? Add more pasta water. Too thin? Let it simmer another minute.

Add your drained pasta directly to the skillet with the sauce. Toss everything together using tongs or two forks until every piece of pasta is coated. Add more of that reserved pasta water, a little at a time, if the sauce seems too thick or starts to look dry. Toss in your cooked chicken pieces. If you're using cherry tomatoes, add them now - they'll warm through in the hot pasta. Fold in the fresh spinach and watch it wilt in about 30 seconds. Stir in the grated parmesan cheese and a squeeze of lemon juice. The lemon brightens everything up and cuts through the richness. Toss one more time until everything is glossy and well-combined. Taste and adjust - need more salt? More pepper? More parmesan? This is your dinner, make it how you like it. Garnish with fresh basil leaves and serve immediately while everything is hot and creamy.