For the crab and chile filling: Heat the butter and olive oil in a medium skillet over medium-low heat. Add the jalapeno, Fresno chile and shallots; season with salt and pepper. Let sweat for about 5 to 7 minutes, adding the garlic during the last couple minutes. Raise the heat to medium, add the sherry (to deglaze the pan) and let bubble until almost evaporated. Remove from the heat and let cool to room temperature.
Add the crab, herbs and chile-shallot mixture to a medium bowl. Season generously with salt and pepper; set aside.
For the Mornay sauce: Melt the butter in a medium pot over medium heat. Sprinkle in the flour and mix with a wooden spoon for a few minutes to make a roux (it should look like wet sand). Whisk in the milk, making sure to scrape the corners of the pan. Bring to a simmer and cook for a few minutes. Season with nutmeg, salt and pepper, and then remove from the heat. Add the Gruyere and stir until fully melted and combined. Add about a 1/4 cup of the Mornay sauce to the crab mixture to bind.
For the ravioli: Place a sheet of pasta on a work surface. Fold it in half the wide/long way to make a slight crease down the middle, then lay back out flat. Place 1 to 2 tablespoon-size dollops of the crab mixture every few inches on one half of the pasta sheet. Brush a little water on the border of the pasta sheet and around each ravioli. Fold the top half of pasta sheet over to cover the filling, squeezing out as much air as possible (so they don't pop open in the water). Use a knife, pasta roller or ring cutter to cut out the ravioli. Dust with semolina and reserve on a parchment-lined baking sheet. Repeat with the remaining pasta sheets and crab mixture.
Bring a wide shallow pot of salted water to a boil.
Warm the remaining Mornay sauce in a large skillet over medium-low heat. Use pasta water to thin to the desired consistency as needed.
Cook the ravioli in the boiling water, in batches if necessary, until they float to the top, a few minutes. Transfer the ravioli straight into the skillet with the Mornay sauce and toss gently to coat. Place 3 to 5 ravioli on a plate and spoon a little more Mornay sauce on top. Garnish with the chopped herbs and lemon zest.