Step 1Heat the oven to 300 degrees. Steam the cauliflower over high heat until quite tender, 7 to 10 minutes. When it's done, you should be able to crush a floret between your fingers. Undercooking the cauliflower will make the custard grainy. Remove the cauliflower from the heat and let it cool for 10 minutes. Reserve 4 florets for garnish.
Step 2Transfer the cauliflower to a food processor or blender and pulse several times to grind. Add the heavy cream and puree until fairly smooth but with tiny pieces of cauliflower still evident. Pulse in the eggs, salt and nutmeg.
Step 3Strain the mixture into a large measuring cup. Stir the puree with a rubber spatula to help it flow through the strainer, but do not press it; this will also make the custard grainy. Divide the strained puree evenly among 6 half-cup ovenproof ramekins. Discard the cauliflower remaining in the strainer.
Step 4Arrange the ramekins in a large roasting pan and place the roasting pan in the oven. Pour boiling water into the roasting pan to come halfway up the sides of the ramekins. Bake in the water bath until the center of the custard just barely jiggles when the pan is shaken, 35 to 40 minutes.
Step 5While the custard is baking, prepare the topping. Mince the garlic. Heat a small saute pan and melt 1 tablespoon butter. Add the garlic and bread crumbs. Cook over low heat until the crumbs turn golden brown. Remove from the heat and set aside. Slice each reserved cauliflower floret into 3 pieces from top to bottom to form a floret profile. In a separate pan, melt the remaining 1 tablespoon butter. Cook the florets until golden brown, then remove and drain on paper towels. Set aside.
Step 6When the custards are cooked, remove them from the water bath and let them stand at room temperature for 10 minutes to set. Sprinkle the bread crumb mixture evenly over the 6 ramekins and place 2 floret slices on each ramekin. Serve immediately.